@cyaoeu any UK2Node subclass or Blueprint callable function can be spawned in this way (for functions you use ClassName:FunctionName, for nodes you use NodeClassName, in either case the ClassName should not have the A/U prefix on it). You can copy a node that you want to be able to spawn into Notepad to get the necessary names. The workflow isn’t super clean but this isn’t really exposed as an end-user-extensible feature anyways.
I’m not sure why you’d want a letter+click to add a reroute node when you can just double-click on a wire to add one, and have no plans to add letter+click for it in the future, but even so, it shouldn’t crash when placed that way (which is really no different to placing one via the context menu “Add Reroute Node…” option). Do you mind starting an AnswerHub ticket for the crash?
Cheers,