[Property Sections] Validate the syntax of complex expression or disallow direct editing
AFAIK, input validator are responsible for syntax checks and alike,
whereas the validation on save is responsible for more complex tasks
such as symbol checking.
However, the sytax checking is only “really” performed for integers and float data types. For enums, or structs, arbitrary strings can be entered. This causes a suboptimal UX.
Either implement a syntax check based on the expressions, or just forbid editing in these cases and just disply the result from the edit dialor
(from redmine: issue id 3585, created on 2018-11-30)