@Corjan-Meijerink I always navigate routes with a lot of shaping and some via points. That's why I find ETA toggle interesting.
After your comment I've done more navigation testing, in my 'Silverfox H1+' on a 'DMD 865x' tablet, and I found that I'm just able to toggle ETA modes with short-pressing (+)button in F1 mode via cable connection (!), but that's useless because in that setting nothing else works in MRA (the proper setting being F2 mode via Bluetooth).
I can't remember where I read that ETA toggle function was usually thriggered by long-pressing (-), but maybe I'm wrong.
If you say that C1 works fine, then I think there must be differences between C1, H1+, etc. and if so this could be solved by either unifying buttons coding between them or creating different Silverfox profiles in MRA settings. Or you'd better check this talking directly with Riku, because all this issue is in fact like a blackbox for me.
I'm sorry for bothering you too much with this matter, and thanks for your attention.