Doesn't seem to do anything at all. Neither the Alt-U nor the Alt-Shift-L shortcut does anything, and there is no visual UI to activate it.

The idea is good, but it has numerous issues. Half the time it doesn't work for inserting a character via enter. For example the youtube comment box. Here on AMO, the Unicode Keyboard panel doesn't even appear properly only the search field, the rest is out of screen in a tiny box, no wider than the search field.
On gmail, it doesn't do anything. Apparently gmail hijacks the hotkey for the addon.
At least an option to leave open the panel when inserting a character would be nice.

Doesn't work on mac

This does not work at all!

On Windows:
- Pressing Alt-U in a single-line input does not do anything. This would be very useful in apps like Trello (for the card title) or forums (for the post title).
- Pressing Alt-U in a multi-line textarea opens a tiny input labelled "Search by name" in the lower right corner of the viewport. When entering anything there (e.g. "arrow" or "dash"), nothing happens. I suspect the dialog is positioned outside the screen.

On Mac:
- Pressing Alt-U inserts the 'COMBINING DIAERESIS' (U+0308) character, which seems to be the normal key mapping on my Mac for this key combination. The hotkey needs to be made configurable, or changed to Ctrl-U (which seems to be available) on Macs.

the plugin installed successful ALT+u open it but
on whatsapp web appear behind the page and cannot work
on facebook it scatered between page blocks and not easy to choose char between other facebook items, but if you manage to select it it will not be inserted
on google and gmail search box it will insert but not all times, but when you write msg it cannot because when focus on it the msg panel collapse and will not recieve insertion
always ugly appearance