I use both handbrake GUI and yt-dlp GUI. Here's something they both do horribly and I would suggest for any CLI tool with a GUI wrapper: have a persistent textarea at the bottom of the GUI that shows the equivalent CLI call to the settings I select in real time. This will teach the user how your tool works and also give GUI-only users a taste of the power they could have if they used the command line.

So basically, treat the GUI as a stepping stone to helping the user build scripts/workflows around your CLI. That way you are only developing the CLI, and the GUI is just a helper app. The second you start adding features to the GUI that can't be done in the CLI, you are now maintaining two separate apps.