Sometimes I copy text from the buffer in VM and I want to use it in an editor command.  Is there some way to paste it from a register into the command text using only the keyboard?
Is there a way to paste text from a buffer into your command using just the keyboard?
command line;register
Yep, just like in insert mode: Ctrl-R followed by the register name, or  for the default one (i.e. Ctrl-R ). See :h c_CTRL-R.