How to make Thunderbird keep multiple versions of a draft?

How to make Thunderbird keep multiple versions of a draft?

I'd like to save multiple (successive) versions of a long letter I'm
composing in the message window. The problem (for me) is that pressing the
"Save" button can only replace the previously saved composition (of my
message). Also auto-save rewrites the draft(s), which seems preventable
with an addon.
So my original question is: How could I make a new draft/concept without
overwriting a previously existing version (which I'd like to keep for
myself)?
I've found out that saving to "templates" creates successive version.
Though this seems counter-intuitive to the suspected meaning of
'templates'. So can I get the same behaviour for the standard "concepts"
folder?
I also wonder, is there any way to save successive versions noted by the
auto-save..? Or (not to make my question too XY), is there some better (or
at least good) approach for keeping track of the genesis of my message?