Add warning that expert mode key maps may not work on other devices

[jambl3r]

expert mode [...] key maps have some easy to overlook disadvantages when not strictly necessary: they are not transferrable across devices

Wow, good to know! For me, that's the biggest disadvantage out of the three you mention, as most of my key maps apply to all Android devices, and keeping them synched becomes more of an hassle with every additional difference.

If Expert Mode maps cannot be transferred across devices, that fact should really be stated in-app, to prevent users from wasting too many hours converting everything to expert mode (provided they're OK with the existing Important! warnings).

Originally posted by @GfEW in #2076

[sds100]

I think I can safely implement it such that they are transferable between devices. The expert mode triggers can have the same options (this/any/specific device) as normal triggers.

[GfEW]

I think I can safely implement it such that they are transferable between devices. The expert mode triggers can have the same options (this/any/specific device) as normal triggers.

I think that combination makes sense, both in terms of efficiency, as well as UX consistency.