Dear Andrew,
there's no UNO API available for the Basic IDE, neither for accessing
any Basic IDE components, nor for extending the Basic IDE.
The Basic IDE can only be extended by modifying the C++ code, which
can be found in the module basctl. As you've already assumed,
the only documentation
I submitted issue #i49239#.
There's a relation to #i48147#, but that's a different problem.
#i48147# describes the problem, that junk.sxc and junk.ods
have the same display name in the Basic Macro Organizer, because
the extension is not part of the display name.
Thomas