Add Sidenotes to every file. Sidenotes are sidecar files in a custom directory

sidenotes.vim

" let g:snotepath = '/path/to/your/sidenotes/'                
" let g:snoteext = 'md'                                     
 
" defaults for sidenotes-directory and extension
if !exists('g:snotepath')
  let g:snotepath = $HOME . '/sidenotes/'
endif
 
if !exists('g:snoteext')
  let g:snoteext ='markdown'
endif
 
if !isdirectory(g:snotepath)
  execute 'silent! !mkdir -p ' . g:snotepath
endif
 
function! sidenote#file()
  let g:snoteref = expand('%:p')
  let b:snotefilename = substitute(expand('%:p'), '/', '%', 'g')
  let b:snotefile = expand(g:snotepath . b:snotefilename . '.' . g:snoteext)
  if expand('%:p:h') != g:snotepath 
    if filereadable(b:snotefile)
      execute 'vsplit ' . fnameescape(expand(b:snotefile))
    else
      execute 'silent! !touch ' . fnameescape(expand(b:snotefile))
      execute 'vsplit ' . fnameescape(expand(b:snotefile))
      silent! put = 'Sidenote for file: ' . expand(g:snoteref)
      silent! put = ''
    endif
    redraw!
  endif
endfunction
 
command! SideNote call sidenote#file()

sidenotes_status.vim

" statusline indicator for sidenote
" to include indicator to the statusline insert following line to
" ~/.vimrc
" set statusline+='%{SidenoteStatline()}'
function! sidenote#statline()
  let g:snoteref = expand('%:p')
  let b:snotefilename = substitute(expand('%:p'), '/', '%', 'g')
  let b:snotefile = expand(g:snotepath . b:snotefilename . '.' . g:snoteext)
  let g:snote_availible = ''
  if filereadable(b:snotefile)
    let g:snote_availible = '[SN]'
  endif
  return g:snote_availible
endfunction
 
set statusline+='%{SidenoteStatline()}'