I do not know if these ideas are repeated or not, honestly haven’t checked much of the ideas shared but the ones I’ve read were not like these ones, so here goes my 50 cents:
- Improving the UI page builder in a way that makes it easier to work with dozens or even hundreds of devices, in a way that we can quickly duplicate one item (without codding) and quickly change the respective item
- Having bulk options to set in things and items, selecting multiple ones at the same time and setting attributes and other options at once instead of getting in of each one to set options (this would save a TON of time with large installations)
- Have the possibility to view more details (maybe as an “admin view”) both in things and items listings page
- Having the possibility to add multiple things at the same time and customizing them at the same time (for instance, in a table like format where we could select the ones we wanted and for each line, customize whatever we wanted)
- Possibility to create more than one “startup page” so that we could use in the APP as homescreen, for different tablets for instance
- Possibility to add different users and set custom permissions to certain pages and even certain options (like this, we could set a user that would have access only to a specific page, let’s say, Guest Room, where that room would have a tablet with only things for that room and bathroom, no access to anything else, this could also apply to hotels)
- Having a user management page where admin could see common things about those users like last login, last item used, we could even keep a log of what each user did (perfect to debug eventual “user problems”)
I have some more ideas but I’ve noticed similar ones were already shared, so I keep these here for now. 
These were based on experiences I had already using OH in the past, which I’ve been doing since OH2.