When copying and pasting one file, a very useful button "Suggest a new name", appends (or increments) a number, e.g. "file 1.odt" "file 2.odt" etc.

Is there a way to change the space which placed after "file" and before "1" to a different character such as an underscore?

Many thanks in advance for any suggestions.

I'm afraid this is not possible, sorry about that.