I'm not sure if you are trying from your computer or phone but I just tried now from my computer and had no problem on my end. I clicked "Add Note" which for me was on far right side. After my note is added "Edit Note" is under item itself. I left the page and came back and it is still there. There was a different post but poster had said "See sellers other items" was no longer on the far right, for me it is still there and I had no issue either.
There have been a number of weird glitches lately that seem to be okay for some but others are having problem with. I am using Safari on Mac computer. With some of the other issues people were posting there is a range of browsers being used. Seems they are focusing more and more on phone use so if you are using desktop (if you're a dinosaur like me) things have been more wonky.
Like you say it would be nice if someone was working on all these glitches and when there are new changes they worked for everyone...like the good old days!
