how to unindent in vim without leaving edit mode?
Type Ctrl-D on your keyboard, removes one tabstop at a time, works for space-replaced tabs.
In Vim in Linux you can unindent multiple lines by using V to select your first line. Press the down arrow to select multiple lines. Then type < to unindent all of the lines.
If you want to indent, type > instead
Backspace will remove one level of indent at a time.