It depends on the task. E.g. FoxPro 2.6 is basically proto-RAD, complete with visual form and report designers and an online help system, but it's too high-level for systems programming. Borland Pascal 7.0 is probably the sweet spot of power and convenience - no visual designers, but you get Turbo Vision for TUI, a very nice integrated help system, and decently powerful object-oriented language. Better yet, early versions of FreePascal that targeted 32-bit DOS.

I don't think any of these would fit on a floppy, though; you'd have to unwind a little bit for that. Say, Turbo Pascal 5.5?

Fasm comes with a cute small DOS IDE.

Or ditch DOS and embrace Wirth's Oberon (the OS and language).

There is a one-floppy build.

Somewhere, I have a printout of the (quite slim in terms of page-count) Oberon manual --- turns out there is a Pi build:

http://pascal.hansotten.com/niklaus-wirth/project-oberon/obe...

will definitely have to experiment with that.

EDIT: but it's apparently an emulated version?

Perhaps:

https://github.com/MGreim/ultiboberon

is better?

For nice, you might be interested in DJGPP/RHIDE. It's somewhat more than fits on a floppy disk though.

https://www.delorie.com/djgpp/.

Maybe Borland Turbo C? I also think Visual Basic for DOS had a text-mode UI editor.

Indeed VB for dos had a UI designer with buttons, forms, dialogue boxes etc.

Or Turbo Pascal...

Or the maintained open source alternative Free Pascal and its Free Pascal IDE.

FreeDOS can also be put on a USB stick so you are not necessarily limited to the size of a floppy disk.