It's advised that you shouldn't make huge changes to your lists in case it messes with the restoration process the devs are doing.
Please read the FAQs, both posts have all the information you should need, I also recommend reading the comments (yes, there's a lot, but there are relevant answers to questions and concerns you may have), reading them will clear up any confusion and also reduce repeated questions that have already been answered :) with that being said, reading lists are currently in the process of being restored, it's just taking a while since there's so many of us, and so much manga. It is advised that you don't manually change your lists a significant amount to avoid any possible risks impacting the restoration progress of your lists.
https://www.mangago.me/home/mangatopic/21080691/ https://www.mangago.me/home/mangatopic/21092806/
Ahh, maybe? The FAQs do say small changes like adding a couple manga shouldn't matter, so maybe not? It could be due to if you've rated manga maybe? Non-rated manga is coming later. I will say, I personally panic added 300 of mine and my 'already read' list continued to be restored afterwards, so I don't think theres anything huge to worry about - it's just about reducing risk to an already broken list, if you get what I mean?

I was gone about 2 weeks or so and when I came all of the things in my reading list was gone and many of it had went to the already read list and I’m adding them again but it’s so tiring I had like 2000+ manga on read