Back when I still made ANSI art, a couple of UNIX Ansi art editors were around, but I used ACiDDraw [1] in (probably, don't remember) Dosbox.

Kind of like I used hkSFV for a long, long time. No GUI utility came close, feature-wise. Although if you consider CLI, you can do scripting after download.

[1] https://archive.org/details/aciddraw