@jayfella, this is awesome.
Not priority, but maybe the gui could be spiced up, maybe something such as this
And another thing, this is like an editor rather than an IDE, but still maybe you should do like Godot engine and still have some support for scripting, maybe Groovy or Kotlin, that way people can still spice up smaller details like Lemur GUI. The more important and core Java code will be edited in the user’s IDE of choice of course.