Hi, just some feedback on this.. We wasted some cycles due to this very issue. Worth pointing out is that dashes ( - ) and dots ( . ) are not allowed as environment variables when using bash, so when someone defines a custom tool eg. PYTHON-3.4.0 then the variable the custom tools plugin exports isn't actually usable.
It would make sense if you guys changed the tool to translate dashes ( - ) and dots ( . ) to a valid character, ie. underscore ( _ ).
Possibly some of your users are having this problem, not realising that it is because environment variables are invalid from a shell perspective.
Secondly, renaming custom tools is a bit dangerous, since if a project has one of these tools used, it won't find it and just pick the first tool ever defined, whenever a project configuration is updated...which can be some time after the actual custom tools definition changed. Not sure how easy that is to fix.