I am diagnosed with ADHD and I believe you can mask as well. I also think people can accommodate their difficulties to appear mainstream.
I would lose everything except my coat, car, bag, keys, laptop case etc all have an AirTag in them which my phone can track. I don’t lose my phone because I have my watch attached to my wrist which I can use to buzz my phone. My watch is full of constant reminders which are set to notify me at the right time to be able to action them and because otherwise I won’t remember and I won’t do these things. To an outsider, I look organised as a result.
I need to fidget but I do this by twirling and crossing my toes. If I am tightly sitting under a desk, I might twirl my ankles or flap my legs. This can’t be seen so I don’t look like I fidget. If the need to fidget is greater, I might play with my hair by putting it up and taking it down again. This isn’t obvious enough to really make anyone think otherwise. If I’m on a Teams call, I will doodle out of sight.
I exercise a lot. The concentration it takes to keep still means I can’t really focus on anything else, including what people are saying. However, I learnt that teachers expect you to stay still and will tell you off for not doing so, but they roll their eyes and leave you alone if they think you are dim and can’t understand. People pleasing and wanting to conform is strong in girls with ADHD. They mask to get there.
My friends had crushes and hobbies I didn’t really understand but you wouldn’t know that because I would copy them and pretend the same. That’s also masking.
As an adult I have all kinds of extra help to be normal. Thanks for my cleaner, my house is clean. Ditto to my gardener. I’m still disorganised and chaotic in my head but I don’t come across that way. I pinch myself to distract me from interrupting conversations and have all kinds of other tactics to be normal.
Then after being sociable and looking completely normal, I’ll retreat home and curl up in bed with my cat for hours because I’m exhausted from masking.