"Restore placeholders" command
Populating a text layer stores the original content of the layer as meta data. This way, it's possible to "re-populate" easily.

It also means that once populated, a field now has its original content and placeholders forever. So entering new {placeholders} manually into the text layer doesn't work – it will always use the stored values.

a solution: a "Restore placeholders" command that inserts the initially used content/placeholders back into the text layer and gets rid of the meta data. now changing something should allow for a fresh start. 
