Is there any way to insert a space in normal mode?

:nnoremap space i<space><esc>

Then, any time you type space in normal mode, it’ll insert a space at the cursor.

Or you could just hit iSpaceEsc.

OK, OK. If you really want to use the space bar in normal, add <> to the above.

:nnoremap <space> i<space><esc>