Okay, will definitely implement the custom property thing.
Here's my logic on it.
If you were in any other IDE, you'd expect your interface to follow what the rest of the system was doing. You'd expect it to match. (xCode for example) - Apple have been going to great lengths to stamp out custom theming as much as they can for example, as they wanted the programs to match the system.
You'd only specifically opt-out of following the rest of the system and the matching IDE if you wanted to implement a custom theme.
For example, like various music synth programs that have a completely custom interface - they've opted out of following the system scheme and purposefully programmed their own interface. These are the exception though, and not the norm.
This was my logic with the theming. The IDE should match the OS where at all possible (and should at least have an option where the user can choose to match the system theme as closely as possible) - which it does - hence my options of appearance mode choices. You can match the OS (manually), or you can at least test what your stack would look like in light / dark mode.
If developers want to opt out of that, as a special use case for example like the synth programs I mention above - or even toast / nero, games, anything really... Richmond's Devawriter stack for example... then perhaps I'll simply add an option to that appearance menu the user can choose called "ignore chosen IDE theme in this stack". That way you could apply it to
your special use case - your tools, where you perhaps always want it in dark mode, as you are [potentially] overriding what the rest of the system and IDE is doing if the user has the rest of the system & the IDE in light mode.
In the same way that you set an itemdelimiter - you don't automatically assume that its set to , or / instead you intentionally specify it so you know it's set correctly. Same logic with designing an interface? If you want a custom appearance, you'd either set these colours with the inspector or in script, and choose "ignore chosen IDE theme in this stack".
If your stack absolutely had to look the same across all platforms, surely you'd specifically set it that way, rather than gamble that the IDE would set it identically for each platform (because it won't) - consider all the possible themes a linux user might have installed for example.
That was my reasoning - there was logic to it, I promise