Thank you for your post.
I have received your screen shots and database file. I will post my findings publicly after all research is completed.
1. open file with existing Tab Control
2. rename TAB names in layout mode
2.a. click on [change] button (German version is "umbenennen" )
3. switch to browse modejust changing the name doesn't execute/save the change. Did you:
Sorry for the late reply.
The notes from Development and Testing are a bit cryptic. In essence, if Sample Data is turned off, then the tab titles appears as expected. The calculated tab names were added without doing a file format change, so either choose to use the calculated tab names and prevent the solution from being modified in FileMaker Pro 12, or you use the non-calculated tab names to gain the ability of modifying the solution in both FileMaker Pro 12 and FileMaker Pro 13.