chooser with dvbt modulation

[F4fdw]

Hi
I make a receiver with RTLSDR and I would like to have the choice between QPSK, 16APSK and 64APSK with a chooser block for example and the same thing for the FEC but in the demod ref blocks. signal, DVBT demap etc .. the menus are drop-down and cannot be controlled by a chooser, we cannot put a value in these blocks, is there a trick to choose the constelation online.
thank you in advance
f4fdw Laurent