Normally, you can specify a category for variables. Eg. typing “Some Category” in the category field, then recompile the blueprint will place it under that category in the properties pane:
However, if you name the category the same as your blueprint
The moment you hit enter, the category field will reset to “Default”. However, recompiling will make the variable show up in the category you specified:
However, it doesn’t store it in the category field, nor category history, so you have to retype it for each variable.