I want code to right click context menu on a file and if it is a .mp4, then convert that to a .mp3 of the same name
also include an option to play faster by +25 +33 +50 or slower by -25 -33 -50 (in a sub menu)
I understand this is different depending on your system, so answer how to do it for the people who use the same system as you
Well, more choice is a good thing. So long as the configuration file stays available as well (because it makes it way easier to script this configuration), then having a GUI available is cool, too.
Having said that, the particular feature that OP wants is for people who want to script things, meaning most of them will prefer the configuration file anyways. You’d need quite a lot of spare devs for one of them to get bored enough to want to develop a GUI, which will not see much usage.