AIBU to dread DH working from home with a toddler underfoot?

This. I wouldn’t have time for his faffing about and popping in and out, of course that’s going to make it much harder for your daughter!
If you put music on downstairs, does that help? Some sort of background noise anyway, just to dull it a bit.
Otherwise I guess going out quite a bit would definitely help, but I can see why you don’t want to be out all day every day!

Is he in an office in the house or a communal area like the kitchen?
when dh worked from kitchen table it was hard going as I still had to make food etc. once he was upstairs in his office it was fine. He only comes down for lunch / occasional coffee. I maybe see him 3 times in 8 hours . You could negotiate timings for when you are out if he’s amenable

We stayed in a flat my husband was nightshift we went out everyday

You don’t need to keep the noise down though, he’s working from home because of an injury. DH and his company will be aware that life goes on around him, I don’t make my DC by any quieter than normal for the benefit of DH working from home.
He’s not trying to hide that young children live with him, why would be?

I think you’re taking this a lot more seriously than it needs to be. You and your child go about your day like normal, if the transitions are hard you tell him not to pop out to see you unless it’s a lunch break and he’s going to interact with DC properly. There’s really nothing else to do.

You shouldn't need to creep round all day. He just needs a headset for calls.

Maybe I'm just lucky but DH has never made him WFH my problem.

That's basically hostage conditions

I still don't get why you feel like you're in the way though. So you and DD are playing in the living room, he comes in to get a drink, says a quick hi, back to the office. How are you in the way?
My DP sometimes has video meetings at home (small box room/office upstairs; living areas are downstairs). Sure, I can hear him, but it doesn't mean I can't get on with stuff or make me feel like I'm in his office.
You seem to be fretting a lot about this.

Can you ask him to get organised with snacks and drink making things (spare kettle, mugs, tea bags and milk etc) in the room he's working in so that the only reason he needs to leave the room is to use the toilet?
Then go out for a bit when he installs himself so when you return he's 'disappeared'. 😂
Not sure what you can do about her hearing him but the less she sees him the more easily she'll be distracted from wanting to see him, I guess?

It's difficult if they're not used to it. I had a period of time when DD1 was 2 and DD2 was 6: months when DH was working from home and DD1 struggled to understand that daddy was working and couldn't play.
We spent all morning out swimming, soft play, park, going for a walk, playgroup and then we would go home for lunch.
Then we'd spend the afternoon at home DD2 usually napped and DD1 and I got to play with her toys or in the garden and DD1 loved our 1:1 time (though I understand it's different for you). About 3 we'd usually go out again for another hour or so, even if it was just shopping.
DD1 got used it within a couple of weeks although I agree you could take him to work if it's too much of an issue.
Or do two activities per day and have a chilled out or quiet time after lunch.

with the best will in the world I do feel like I’m in the way in my own home.
Is your house small? Isn't he in one room with the door (potentially) shut? Why do you feel like you're in the way if you have space and he's shut away?

So why go out for so long? I often didnt go out with my daughter for several days at a time. We had so much fun at home that it really wasn’t necessary for us to go out all the time.

I understand your difficulties OP. DS struggles with transitions, and at 2 he would have a meltdown if things didn't go to routine or as expected.

What helped us when people were working from home wasn't to say "mummy/daddy is working, she/he can't play" was "let's go play and mummy/daddy will come and find us when they're ready" and "shall we make something to show them when they find us?" "I bet mummy/daddy would love it if we made them a cup of tea at (whatever their breakfast time was), shall we make it together, you can put the teabag and the sugar in, I'll put the water and the milk in and then we can stir it together" or even "shall we make a tea party for (break time)" and literally getting the child to make what is essentially sandwiches for lunch and a jug of juice to sit on the floor with.

The coloured sign someone else mentioned is also a good idea.

We have a cheap pound land clock that we have colour coded parts of the day to, like breakfast, quiet/reading time, play time, etc. Maybe something like that could be a good visual representation for when daddy will be ready to play, if you can schedule mummy playtime and daddy playtime. Children don't really have a good concept of actual times they live in now, or later, so being able to see what is now and what is later can be very regulating.

You’re talking as though you’re the only person who has ever had to look after a toddler at home all day while their partner is WFH.

YANBU

My DH wfh except for the occasional one day in the office every few months. I have a 2 yo who refuses to nap 95% of the time, doesn’t sleep through the night as of yet, climbs on anything and everything and I have to be on constant alert. They know where DH is at home. They don’t have to hear him because they are used to seeing him in his office and will easily run off and go to see him the moment my back is turned. When he’s not home, it’s so much easier. We have our own routine and we run errands, go to the park and go to the library often but stuff still needs to be done at home and even then I’m trying to stop them from making more mess which results in a tantrum every time I do so.

I can tell them until I’m blue in the face that daddy is working but that doesn’t mean they understands what that means. I’ve been telling them since they could climb stairs so over a year now.

Tbh, he doesn’t help the situation because he will allow them in certain times and not have them in during other times.

Luckily they start nursery next month.

At least it’s temporary for your DH.

I think after a few days of redirecting she'll be used to it. Just have really clear boundaries - no going upstairs or no going in that room or no banging on the door or whatever makes sense with your layout.

As others pointed out, many of us had to navigate this during covid with no option to go anywhere at all so you at least have all that on the table. Morning home playing with whatever, lunch, out to the library / park / soft play / whatever, home for dinner. No need to be out dawn to dusk!

I think you're overly worrying, it's very common for families to have 1 parent WFH. Just get out as much as you can, surely you'd want to anyway as such a lovely day. I'm barely home with my toddler.

No quite! I think you’ll just have to consistently reinforce that daddy is working and you’ll see him soon.
I asked if you could drop him to the office and pick him up again. Is that practical?

I was referring to previous posters who had been suggesting that the OP goes out! And whilst your little one was fine with your husband working from home, the OP stated that right now her little one isn’t fine with it and she has a battle to keep the child away from where he’s working and that results in tantrums. No doubt disrupting her husband, especially if he’s in online meetings etc.
Of course people play with their children but you totally missed my point.

You say he's normally out Tue-Fri. Does that mean he normally WFH Mon & Fri?

If so maybe you need clearer messaging.
She will get it over time, like every child had to in lockdown. Sign on the door is a great idea. We would also keep doors shut so downstairs doors & stairgates prevent her climbing the stairs, and parent working behind a closed door upstairs, so she can't even get to the "office" door.

Make her a little "now and next" board: play with mummy, lunch with mummy & daddy, playground with mimmy. We've been pointing at pics of who is looking after DC with ours since they were babies.

I would make a game of it and keep repeating that daddy is working. After a few days it will become habit that he can't be disturbed.

My dh has worked from home for 13 years. All mine have grown up with him home and it’s been wonderful for him and them. I can’t see the issue. You say “daddy’s busy” and redirect/ distract.

And message any mum friends around begging for a favour to camp at their house for a bit! Obviously returning favour when he’s back at work