Running 2.4.0 on Linux Mint 19 and bleeding edge (source pull) gpredict and hamlib.
When in new QSO screen with Satellite tab selected there is a space for "RX Frequency".
Above on the same screen is the Frequency that is read in from the radio that IS the RX Frequency.
Since all (assumption) satellite work is done in split mode, can you not use the hamlib get_split_freq to get the TX frequency?
That leaves the question, Shouldn't the space on the satellite tab be "TX Frequency" and could it not be filled in automatically with data from get_split_freq?