I suggest to change the frequency step size for USB and LSB from 100 Hz to 50 Hz.
This makes a noticable improvement when tuning signals for best voice quality.
I make this change every time I download the software, in file src/applications/gqrx/mainwindow.cpp:
case DockRxOpt::MODE_LSB:
...
click_res = 50;

(same for USB)

Of course even better would be to have some setup of custom step size per mode in the user interface but that would involve more work.