Custom folding region based on code

I am wondering if it's possible to define regions based on the code in the editor. For example, in PlantUML, all diagrams begin with “@startuml” and end with “@enduml”. I want to define those two lines as region beginning and end blocks similar to how PyCharm can automatically create regions based on indentation in Python or brackets in JSON.

I know I can just highlight and define a region, or I can add the custom “region” and “endregion” lines, but I don't want to add additional lines of code if I can avoid it.