Guy with ADHD here. Figured it out Jan 2017 and diagnosed with it March 2018. Since learning of my ADHD I've been trying everything I gain control over my life out so God willing I'll share over time tips I've learnt to make ADHD more bearable to live with.
When I found out I had ADHD, I instantly turned myself into an experiment. Still am I guess. People with ADD are outside the normal realm (enough to have to have their own name) so the rules can be strongly different. The first point of action before experimenting with ADD partner would be to figure out how they work first and what helps people with ADD to control their symptoms and start your experimenting one at a time from there. The main problem from the very beginning is the lack of knowledge/support on ADD and its solutions. If a normal person has a problem, they seek help from another person and keep doing so till you get the right advice that works for you. That isn't possible for someone with ADD. They seek advice from normal people and because their rules are different most times it will end up in failure because it just doesn't account for ADD rules. So if they haven't had specific ADD support their entire life, they will have been severely handicapped from a young age due to the lack of support in exploring themselves in this regard.
So what if you're the ADD's partner and he or she won't experiment with what does and doesn't work? I believe it might work to place your expectations in your ability to manage their ADD and not in them and their ability to. Of course this is if you insist on keeping the relationship for whatever reason. I've realised that if my wife is stressed for example, I usually never need to tell her she's stressed and to calm down. What I do need to do is make her hot chocolate or give her a massage or clean the dishes i.e. reduce her stress through action and not words where you can. Eventually she just thanks me and tells me she was stressed anyhow. Likewise the hope in experimenting is that your ADD partner, when they see the improvements, will want to keep those improvements that way because they see its making their life better and therefore more likely to look up more ADD help. My wife was just as resistant with my insistence that I had ADHD until she saw how much I improved from following ADD & ADHD solutions.
Hope this helps.