Meino Christian Cramer wrote:
If by "buffer" you mean what the Vim docs call a "register", see ":help
for what keyword I have to look in the online-help to find a hint
how to copy any text from a buffer as any part of a command currently
being edited in the commandline ?
If you mean part of a file being edited, IMHO the easiest way is to yank
it beforehand into a register, though in some cases you can use the
expression register (Ctrl-R =) with e.g. expressions such as getline(".")