I would welcome that feature as well.
The “non-mirrored behavior” with Tab and Shift-Tab if the cursor is not at the beginning of the line can be a bit of a struggle: If you re-indent a listitem with Shift + Tab by accident and try to revert it by hitting Tab, you’ll butcher the listitem even more.
Suggestion: Use Tab as hotkey
It seems ideal to make Tab always indent list items¹
- Currently, it always inserts four spaces (or an actual tab symbol).
- Multiple spaces are ignored in markdown preview, so it seems unlikely that any users currently rely on the option of “mid-list space insertion”
1: assuming the Smart Lists feature is enabled.
This change would allow an easy way of fixing list indentations by navigating with Up/Down while either hitting Tab or Shift + Tab.