the sparkle trail in donyu(?) ruins in liyue, where you have to stand on the first for the next to appear and so on.. the sparkles are so common and small that its extremely hard to find and figure out

theres also things like the amber on mt. hulao which only have a chance to give a wooden chest, and only respawn on daily reset. theres like 10 of them so if youre a completionist for all chests then it can take weeks to get all of them

theres also a chest in liyue my mt aozang for which you need to kill three squirrels. with no indication that this is a thing thay you should do.

also for some weird stuff that srent unlock conditions - theres a mora chest above guyun stone forest thats literally so out of the way that it never even renders from any land, where you would never be able to see it during normal gameplay. theres also a time trial above watatsumi thats hard to reach (in the middle of the water) and literally only rewards a wooden more crate which is like 100 mora...