The editor in the mobile app is a markdown only editor. You can still apply all the formatting you need but you have to do it with markdown instead. When sync'd you can still use the richtext editor for those notes on the desktop app as you are currently using and the markdown tags will become invisible.
I take it you aren't familiar with markdown itself? It isn't a menu as such its simply a way of formatting text using text characters.
e.g rather than just selecting text and clicking the bold icon you just type **bold**
which gives you bold text when rendered.
So in that sense there isn't really a need for a toolbar itself, all the buttons do is apply those markdown tags in the background. Even the editor you are using on the desktop app is simply putting those same tags in but you just can't see them. If you hit the "toggle editors" button in the top right you can see exactly what it is doing.