o yes. And it seems that controlling ATEM's via MIDI has become easier with a software called Central Control (Windows only). I will check that out, there's a one month trial.
https://centralcontrol.io/devices/Edit: it appears that the ATEM Minis are not supported
Edit2: they are supported, as it turns out after contacting the developer. This is good news. What I haven't got sorted yet is the mapping. I will create a separate discussion thread about Central Control when I created a working Lemur template for the Mini's.
Edit3: after a few tests finally a success. I control the ATEM Mini Pro with a MIDI controller. And it is bi-directional, meaning when I hit a button on the Mini, the MIDI controller button lights up as well. This looks very promising, also for TouchOSC and Lemur surfaces.