There are some useful features in Lokalize that are not quite obvious. Ideally they'd be more obvious, but here's an attempt to just document them a bit.
I think I'll update this list in the future as I find more of these.
Focusing the translated text field
There isn't currently a command to focus the text edit field. But the functionality is there. Use the Ctrl+l shortcut (“Focus the search line of Translation Units view”) to focus the filter field; while in the field, Esc is set up to move the focus back to the edit field for the translated text.
I literally only found out about this after reading the code. This could be a result of me being willing to dive into the code, but I don't think I would be able to find it otherwise. In !253 I made it so that this is at least mentioned in the docs.
Ideally this should probably be a standalone action because this default keybind breaks if Esc is bound to any action. I might work on it if I find the time.
Opening just untranslated files in the Project Overview
Right clicking on a folder and choosing “Open selected files” will open every file in the folder. But there isn't an action for opening just files that aren't fully translated.
That functionality is actually there: in the project overview, choose “Hide completed Items” in the toolbar (or in the menubar → “Settings” → “Hide completed items”; or with a keyboard shortcut, Ctrl+t by default), and then “Open selected files” will only open the files that are visible.
This is non-obvious since it requires connecting the dots between hiding/showing completed items and which files are opened.