I accidentally clicked the "hide usage note" button instead of the heart icon for a usage note in the dictionary view (on mobile, these buttons are quite close together). I clicked the eye icon again to un-hide it, but after I reloaded the page the note was gone and there doesn't seem to be an option to restore or view hidden notes anywhere on Renshuu as far as I can see. I have two questions about this:
1. Is there indeed no option to restore hidden notes?
2. I tested this behaviour (hiding and then un-hiding by clicking on the eye twice, then reloading the page) on some notes I wasn't interested in later again, and the same behaviour occurred. This seems like a bug to me, since the UI removes the red strikethrough line after clicking the second time indicating that the change has been undone. Can/should I report this as a bug somewhere?
If there's a way to restore a hidden note, I can't find it. I feel like there probably isn't. Looking at the code, you can't unhide it client-side.
When I test it (PC), I can click on the eye icon once to hide (red strikethrough line appears) and then another time to unhide. For me it seems to be working as intended. The note is there when I reload the page. If that's not the behaviour you're experiencing, it might be worth reporting as a bug (on the "Bugs / Problems" section of the Forums).
Regardless, not being able to restore a usage note after you hide it seems like an oversight. You should probably wait a bit, just in case someone has a solution. I could be missing something.
