It's very frustrating when Inventor doesn't accept your parameter name, and then the parameter you started creating disappears and you have to start all over again.
How about, instead of failing to create the parameter because there are spaces in the parameter name, Inventor automatically replaces the spaces in your parameter name with Underscores '_' for you instead?
Paul
Other ideas on improving the parameters manager:
https://forums.autodesk.com/t5/inventor-ideas/parameters-dialog-overhaul/idi-p/4774867
https://forums.autodesk.com/t5/inventor-ideas/overhaul-the-parameter-interface-access/idi-p/3686266?...
https://forums.autodesk.com/t5/inventor-ideas/better-manage-skeletal-models-with-parameter-sketch-fi...