Another couple of things that spring to mind that have helped me recently.
Planning what to do instead - this is hard with ADHD but rather than say, sitting down and making a daily plan what I have found helps here is dividing the day up into sections and then having a list of ideas for things to do in each section.
So for example, when DC want attention I have a sort of "list" I can run down:
Outside time?
Lego
Train track
Colouring
Board game etc
And if I want to half-do something mindless while e.g. watching TV I can:
Jigsaw puzzle
Craft kit
Colouring
Bad sewing (fix holes in trousers, make tiny doll's clothes/doll's house curtains etc)
Paint nails
If I know I need to just stand up and get off the computer
Kitchen/daily task cleaning
Laundry
Food prep
(These are boring, but I use the idea of a podcast to motivate myself)
Knowing when my energy levels are likely to be highest/lowest during the day. For example I have guilt free computer time first thing in the morning. If it's my morning to get up, I get up when DC wake up, settle them with TV/breakfast, change nappies. Then I do my own teeth/coffee and I let myself veg until about 9am. They get up anywhere between 6 and 8 so that could be a couple of hours.
9-11ish tends to be my best time so I aim to "give it" to DC by playing with them or do something in the house. Break for lunch. Then swap to the opposite - or take DC outside as they tend to need exercise, like dogs.
Again, 3pm-4pm is often an energy dip for me. If I've got up really early or had shit sleep then my medication also wears off about now and gives me a huge crash which makes me zombie like. Nothing I can do about that so I do guilt free screen time (for me and DC!)
4pm is then time to start moving on dinner, maybe 4:30 if I'm really sluggish. After dinner DH usually does something with them, I might join in or if I'm just too low on energy then one of my "sitting down mindless activities" while watching them.
Then it's guilt free after they are in bed. But I have another "wind down" routine/rule which starts at 10pm after which I don't get into long MN threads, "just one more round" games, youtube, "just one more episode" TV or research rabbit holes.
Also I went around and around this for years and never quite worked it out but I need things to be interruptible. For example I started writing this post a couple of hours ago, then DC wanted to play so I just left it open on computer, there probably was some period where I would have felt panicky about doing that like "This person needs an answer immediately!!!! The thread might have moved on and my reply might be irrelevant!!" - but this isn't realistically true for most threads. Not that much is that urgent (and honestly, when it does seem that urgent, it's probably a troll thread anyway!)
This is annoying when I come back and write a reply in several sessions and then a thread gets deleted, but oh well. It mostly reminds me NOT to invest a whole lot of time into something that doesn't directly benefit me/people who are important to me.
Quite often literally just the action of standing up and being in a different room makes me look around and think ugh, the bathroom needs cleaning and I need to remind DS1 to get some sunlight and all the other things that I miss when I'm hyperfocused on a screen.