I have a Minilab 25 and iMini working as they should. Rotary encoders will change both switched settings (including waveform or octave shift) and continuous (filter, glide, mod mix, envelope controls.
There are several things to remember. The most important is to select a preset on the Minilab (shift and pad 1 for example) before you do anything else. Now you have base reference. Now open MIDI learn, twist yourself silly setting up whatever. Exit MIDI learn. You are good to go. Always be sure to select the MiniLab preset you used with iMini BEFORE you expect iMini to listen to what it's supposed to know. The issue is not with iMini but with MiniLab waking up stupid and needing to know who it is before it will do what you ask of it.