Yes, it may be able to. At least, Delphi, the idea (and language) of which Lazarus is based on, was written in itself, at least for v1, I've read. Probably for later versions too, because Object Pascal (although IIRC the language is now called Delphi, like the product), is a powerful general-purpose programming language, with OOP support, module (units) support, and even some sort of generics (IIRC) in later versions.

Yes it can do that. That's how the IDE works and displays the GUI designer.

Can you recommend any documentation on the "meta" angle? Most documentation I find assumes the creation of "static" widgets that are activated or hidden at run-time (or at least act that way).

This is for Delphi however it should be very similar for Lazarus: https://stackoverflow.com/questions/1005373/creating-compone...

Nothing magic. Create it, set properties.

Thanks!