Is it worth changing DD's name?

Just explain in the known as box. That she goes by eg Amy her middle name. It won't be a problem.
A child can opt to be called anything. Even if its nothing to do with their name.

I would leave it as it is. My Dad grew up being known as his middle name by the family, his proper first name everywhere else. Never caused any problems. "known as" is common on all forms now, so at school you would list her full name as for example Alexandrina Rose, known as Rosie.

change it or start using the other name now,

My son is (deliberately) known by his middle name. It's more common than you'd think. Schools normally allow for you to put a 'known as' name even if you register them with the full name. You can change a name by deed poll but not sure I can see the point in your case!

I've gone by my middle name all my life, as has my sibling. I have no idea what our parents were thinking.

It's been a pain, to be honest. I often get called by my first name (which incidentally I really dislike) by people who don't know me, and it's on all my official documents which can make things difficult. Also it's not nice being addressed by a name that you don't recognise as you.

I'd change it for her sake, I really would.

So yes, change it

I was going to say leave it but remembered my gran who was known by her middle name. All medical stuff always called her by first and she'd get really pissed off. When she had dementia they just thought she didn't recognise her name

DH is known by his middle name. It is massively confusing....banks, passports, anything official is a headache.
In a recent emergency I had to give the police my DM's siblings' names. However, they are all known by their middle names which made trying to trace them extremely difficult as I struggled to remember what each of them was really called. I think the police thought the whole family was mad!

The use of my "proper" name by work colleagues, officialdom or the general public that I deal with daily helps me to be "in the zone". Then I kick back and go by my nickname with close friends and family. Also, when my parents called me by my proper name, I knew I was in bother

Leave it. I know lots of people who go by their middle name.

I'd change it. I used my middle name, but my first name was on anything official, so any time I had dealings with authorities, they called me by a name that wasn't me. It was intimidating when I was already feeling vulnerable. I changed it by deed poll as an adult and am so glad I did.

Why not leave it for now, but make sure DD knows she can change it herself when she's older and you won't mind?

That way she can choose what works best for her.

Change it.
My DM was known by her middle name all her life but the staff in the hospital kept calling her by her first name despite my protestations. They swapped shifts and kept forgetting to update the paperwork and when she lapsed into a coma, I felt distraught that she wouldn't know they were talking to her when they attended to her needs.
I know she had often previously complained to me that her parents had saddled her with an awful first name (not suggesting OP has) and she wishes they'd only given her the middle name.

We changed our dd name last year, we use her middle name and she wanted it to be official name, so we've just switched middle and first round.

Not sure about it causing problems with Dr appointments etc but I know it annoyed my dd when she got called in by the dentist and Dr etc by the 'wrong' name.

We let the school know that she was known as middle name at school but official reports from school had to come home in original name.

It is your choice, but as one who is known by her middle name I beg to differ from those saying leave it.

I have had a lifetime of explaining, and of having to remember when I must respond to my first name instead of my usual one. I find it a total pain in the arse. I wish that my names were the other way around.

Change it now, while it is relatively simple. I sure wish mine had been changed while it was only on birth certificate and medical records. Now I am 50 and it would have to be changed on so many thousands of things that I cannot face doing it even though I would like to, so I feel stuck with it.

Even my parents do now question why they did it.

I am known by my middle name - similar situation, my parents just never ended up calling me by my first name!

It's annoying for anything official (I also prefer my middle name), doctors, dentists, school (school was pretty annoying I must say!!) and can be confusing for all involved.

I would change it just for things being straightforward for you DD as an adult.

On the hand, my husband is also known by his middle name (first name is a family name) and he's not bothered by it!

Most importantly, huge congratulations OP for the safe arrival of your lovely baby girl!

My dad and his brothers are known by their middle names, mainly because they have obscure first names but it's never been an issue and they are in their 50s & 60s

Primary school principal here - no issue to us at all. Let them know what name you prefer and they'll use that at all times. The only time you'll see it is on official documents.

I know a few people known by their middle names, it's fine. Just tell school she's know as "middle name" before she starts so they can put the right name on things!
My sister is always known as a diminutive of her name, had no idea it wasn't her 'proper' name until she went to nursery and didn't know the name written on her peg.

It's also handy on social media - I can't be found by the public that I deal with every day.

Leave it. My brother is nearing 60 and goes by his middle name. Never been a problem. Ever. And he's travelled the world . He explains to those who need to know it and just shrugs off the use of his first name by any bureaucrat he briefly deals with. No identity confusion. Totally manageable.
By coincidence, my family and friends know me by a nickname and officialdom and work colleagues know me by my official name. No biggie.

At hospital/anything medical she will be called by her first name, disorientation even as an adult.If she joins the police/law/armed forces she has to use her given first name

Nonsense, at hospital she will be called by whatever name she gave them, the one she uses. Same as anywhere else. And you can use any of your legal names in any of those jobs.