If your keyboard controller allows you to easily set the MIDI channel number, you could use the ‘Create MIDI input channel mappings’ in the Wizard. Then you can assign each MIDI input channel mapping to different soft-synth tracks, and thus swap playback of the synths just by changing the MIDI channel on your controller.
If you only have one MIDI input mapping, then you have to drag it from track to track. A ‘global MIDI input’ option is on the plan.