Speaking of simple -- the %M flag in 'statusline' gives you the + for modified files. No need to use an expression block. I like to use the status line to keep

Speaking of simple -- the %M flag in 'statusline' gives you the + for modified files. No need to use an expression block. I like to use the status line to keep track of buffer-local options that differ from the default setting. That's what https://github.com/tomtom/tstatus_vim https://github.com/tomtom/tstatus_vim gives me.