I've tried a couple combinations of --remote and --servername, but I'll give it another go in a bit.

I'll be honest I only use --servername for https://github.com/ardagnir/united-front - which doesn't work well with sending commands as every instance is set to same server to share registers

:open-file-command ["vim" "--servername" "coffee-menu" "--remote" ["+%s" :line] :file] worked perfectly if I start vim with that servername.

Okay, I got columns working: :open-file-command ["vim" "--servername" "coffee-menu" "--remote" ["+exe \"norm %sG%s\\|\"" :line :column] :file]