Comment 11 for bug 927898

>what do we do with the status of the button after one of the 2 toggles has changed?
No, the button and the status of the two are independent: you can have A on and B off so if the button is pressed you'll have A and if the button is not you'll have none. If B is turned on the button doesn't change state. If neither A nor B are enabled, the button has no effect (everything is always disabled).

>MHO we should only consider to give each of the 23 sources an individual toggle, and each of the 38 targets.
Ok, this could be an option. But then I think you should provide to the user some configurable buttons so one can create it's own sets of snapping configurations. This could be an easy solution for both programmers and users. Maybe 3-4 buttons (sets) could be enough.