How can you easily export the "click track" layer in the final file, it is not included in the export in e.g. mp3. You cannot copy this special generated "click track" layer in the master into an additional new layer. How can this be solved?
I'm afraid it isn't possible to export that click track. However, you can add an exportable one to a Rip by copying & pasting a percussion note to the start of each beat, dragging & dropping sounds from the Sound Panel, or (PRO version only) drawing them with the Draw Sound tool. Once you've done this for one bar, you can quickly duplicate them to the following bars by selecting them and repeatedly pressing Cmd/Ctrl+D.
Before doing this, you should ensure that the bar lines are correctly positioned by dragging the tops of them. (Subsequent bar lines update automatically so it's best to start with the first and work forwards through the Rip.)