I feel that any solution where you have to keep pushing the encoder down while turning is a bad idea because it will put unnecessarily stress on the encoders and circuit board. So pushing to switch to a different mode, release and then turning is fine of course. But other people have asked to use the push function for a reset back to the default value of the parameter, so what about that?
A coarse and fine parameter for frequency is common on most eurorack modules. For example my STOs have a coarse and fine knob.
I think I can change the step size of the LFO to 0.001 Hz for example, for the fine control, and with the new acceleration/deceleration code I’m working on for the encoders, this should work fine. That would give us a period length of 1000 seconds or about 17 minutes, maybe long enough?