This is not like the one on Chrome, it just opens a simple embedded window and shows your Google keep's web page on it, which can be achieved using Chrome's standalone apps already.

Idea: Fullscreen button for resizing windows when we open your tool outside Firefox.

The extension is great! I would like to see the same extension, but for Google Photos, to download photos to PC and vice versa

Works great, its very comfortable and convenient to use.

It does what it's supposed to, but I have multiple Google accounts, and it seems to only want to have me logged into one in the little pop-up, and if I log in to a different one it just opens a new tab with that account without changing the main one, which is a bit annoying.

Update 19/08/21: Just gives Google 403 error whenever it's opened. Completely unusable in its current state and I'm forced to open Google Keep normally, defeating the purpose entirely.

++

The fonts are way too small.

Still can't select the proper Google account to be the default. Clicking "manage your account" in the sidebar simply opens the main Keep page for that other account, without an option to change the default. Very, very basic functionality - how was this not the first thing you nailed down?