Support for the mode switch was added to OpenWrt master and 21.02 - I would like to ask, which position (left/right or dot/no dot) corresponds to BTN_0 being pressed? (Or alternatively, is the gpio value hi or lo for each position?)
The OpenWrt wiki device page doesn’t say and I don’t have the device to test directly - thanks 
This is what it defines in the default firmware for mv1000
switch_left=$(grep -o "|vpn.*lo" /sys/kernel/debug/gpio)
So the left is low.
I see - thanks 
BTW looking at the rest of that file (/usr/bin/switchaction) it appears that switching left enables functionality (wg/vpn/tor) and switching right disables functionality. On the case the dot is on the right - I would have assumed that switching to the dot (right) enables functionality and away from the dot (left) disables functionality.
I mean from a UX perspective, when there are two choices the one with the indicator (the dot) is usually interpreted to be the on/active/selected state, and the other option with no indicator is usually interpreted as the off/inactive/deselected state. Checkboxes and radio buttons in web design are the most common examples of this pattern.
(If instead the indicator was another shape like an X or a “do not enter” sign, then I think the expectations would be different.)
It’s great that the UI explicitly says which switch position does what. I just think aligning the indicated switch position with turning on functionality would be slightly easier to use. The user can rely on an existing mental shortcut (indicator means “on”) instead of having to remember which switch position does what.
Thanks again for your help (and your great products) 
Yes you are right. There is long debate about this. But eventually we choose Left ON and Right Off.
The main reason is: the switch button default state is put on the left. And we hope that the default vpn status is ON. Otherwise when the user enable this function, the vpn will be immediatelly turned off.
Anyway I don’t there is too much difference.
On Mudi, the setting is Up ON and Down Off.
