There was, can't recall the one that was popular prior to Microsoft adding https://en.wikipedia.org/wiki/DriveSpace MSDOS 6.0

That'd probably be DoubleDisk or Stacker. https://forum.winworldpc.com/discussion/10401/software-spotl...

Stacker was pretty common in the early 90s.

I don't really remember any: my main recollection as an ST user was the format programs that let you increase the track count and the sector density.

I recall the default format was 9 sectors, 80 tracks, 2 sides with 512 bytes per sector = 720KB, and you could push up to sometimes 82/83 tracks and maybe 10 or 11 sectors to get more out of a diskette.

Actually, I think my ST originally came with a single-sided floppy drive and had to be upgraded.

The initial release of Atari's has single sided drives, I think the 1040ST had Double sided though, they did upgrade that shortly afterwards I believe to enable the marketing bods to show a larger number they could compare to the Amiga. So was only early 512STFM systems and those had a red drive light and the double sided had a green one if my memory holds.

Sad thing was, due to the early single sided models, many games would limit to 720k so as to not limit there market. That saw games that would happily fit upon a single double sided disc, cast upon two floppies forcing switching. So that small batch of single sided initial release systems, really did have a legacy impact that lasted for years and did it no favours.