Hi, I was diagnosed about 3 months so it’s still newer to me too.
I have entire days like what you’re describing. Hyper focused, cleaning like a madman, then suddenly the doorbell rings, I bring in the Amazon package and can’t remember what I was doing.
My garage (wood shop) is full of projects at various stages of completion too. It sucks when I finally get time to be out there and have no clue where to start. I’ve also noticed my short term memory is getting worse and worse. Which means I can’t just pick up where I left off yesterday because odds are I can’t remember.
I’ve started journaling with some notebooks from Amazon. They have a dot grid pattern so you can creatively make a plan, log your day (this is my current memory), schedule meals. I even started one just for writing. (I’ve secretly always wanted to write so I’m super excited on that one. Started it Monday and I’m 7 poems in!)
My mind wonders when I hit a point like you describe though; searching for that thing I should be doing or could be doing. Am I doing the best thing with my time? Best advice I have for you is think to yourself “what’s the bare minimum I Have to finish so that I can be done and go do what I want to do?” That train of thought usually helps me focus just enough to get through the overwhelming. Then I either get into my task and keep going, or I’m free to switch to something else.