from my experience in support, a lot of non-power users are copying variables by just clicking them, and then trying to use it in a different flow, or in an unaccesible place
the suggested idea is to make it an toggle in account settings, since this feature is only useful for power users that know about it, and confusing for new users
That seems like it would be more confusing. Maybe instead the first time you paste an invalid variable it can give a popup?
i think it would be less confusing, since they wont know about the feature, so when they click on it they wont try it again, and then do it the correct way, possibly getting motivated to actually try watching an tutorial
and when they would then try manually copying the variable from the field, it would feel ‘wrong’, so they would know that whatever they just did wont work
this click to copy variable feature is only useful for power users