UX proposal for +/- Indent menu commands
Its taken me a long time to discover Zim supports arbitrary indentation: Tab/Shift-Tab indents/un-indents line or selection, including paragraphs and lists. The functionality is brilliant, the UX was very poor from the point of view of discovery.
I realise a menu item is redundant in theory, but recommend you add Format > +Indent (Tab) and Format > -Indent (Shift-Tab) menu items because this provides a simple route to discovery of the functionality. From there it is a short step to discover it works on list and multiple line selections.
Zim 0.57 on Windows 7 (Windows installer)