multiple lines indentation at a time is supported. You have to select multiple lines and press tab (to indent) or shift+tab (to remove indentation).

I like the fact that if you select multiple lines with one line partially selected, it works as expected (selecting whole of the partially selected line)

Windows/Emacs user here. What does these shortcuts do ?

If you have a block of code/text selected, Cmd+[ and Cmd+] shift the entire textblock one tabindent to the left or right, maintaining the relative indent level of each individual line.

Is it different from ctrl+tab / ctrl+shift+tab ? Because these shortcuts works in this editor ("Multi-line highlighted text is also tab-able, and shift-tab removes a tab character instead").

Thanks for your interest! It has been noted. Once I work through the existing backlog of bugs, I'll revisit ideas such as this one.