In MacVim the text that I\'m editing in all buffers is jammed up hard against the left hand side of the buffer. I find this quite visually jarring, especially if I\'m looking at
I use line numbering for that reason (:set number). But if you want a margin without the numbers, use:
:set foldcolumn=<width>
Example:
:set foldcolumn=3
There's also a MacVim-specific option, MMTextInsetLeft, which can be set with defaults write org.vim.MacVim MMTextInsetLeft VALUE in a terminal (where VALUE is the number of pixels in the left margin. There are also settings for right, top, and bottom margin, see help macvim-user-defaults for details.