it is as it is - the online portal of TG lacks sophistication when comparing with others and does not fullfil all customers needs
Therefore -> contact TG or travel agent - then you have someone who can do things as you order and you are not wasting your valuable time with as ystem that most often goes only half way but doesn't bring you to the end where you want...

Was just trying to book a return fligth from Bangkok to Hamburg, but TG's website only offers various midnight flight options but not my preferred daylight connection via FRA....don't know why not (I learned that all flights are available in their computer reservations system)