[This tip is about a Digital Equipment VT220 terminal, specifically, but you can probably use the same idea on other terminals. -JP]
I worked at a university with labs full of VT220 terminals.
VT220s can be set to act as either VT220s or VT100s.
The top row on the keyboard has a key marked
Unfortunately, the key sends a real ESC character only when the terminal is
in its VT100 mode.
As a VT220, that function key sends ESC followed by the four characters
[23~"-these make vi beep and change character case.
You can solve that problem by putting this command in yourfile:
map [23~ mm
Then, whenever you press that key in the VT220 mode, the ESC character will
should and the
[23~ will execute the vi command mm.
the current cursor position as "m"-nothing useful, but
it keeps vi quiet.