Unfortunately you can only have one overarching Trip per pass. Obviously you can still split the pass usage into as many separate excursions as you want, obviously using separate paid exit and entry routes after using your 2 I/O journeys.

Good luck/bonne chance on finding les trains the last part-maybe even that Sofia-IST overnightttrain may already been cancelled again if winter comes and covid hits again. Plus that les trains by TCDD in TR are also very sparse and do not really come anywhere near the Batumi border (I did that several years ago-by overnight bus from Ankara).