I mean UI panel plugin for switching between different outputs, for example, i have 2 sound cards and want to switch between them quickly, not by going to preferences.

Searched the forum, but didn't found one. Strange, because it's quite simple

Or maybe there's a way to do this without any plugin?

As far as I know there isn't such a feature included in foobar nor a plugin available that does this. I think this isn't even possible.

Of course it's possible, you can change it in the preferences -- he's just asking for something a bit quicker.

I second, It'll be a whole lot easier if we can switch output devices through some hotkeys and insert an indicator into status to let us know which device is currently in use.

There is no component to do that. The relevant API is not part of the SDK, so it's not even possible to make one.