A lot of people who use a VFD to power two machines fit a red 3 phase socket on a flying lead and use that to swap over.

If the machines are close some have a wall mounted socket and use two plugs, one per machine.

Big No No is NEVER unplug whilst running, OK to unplug whist plugged into mains and switch on but not running.

One thing to watch when sharing is the motor load in amps as these 'should' be set per motor.
Say you have a 2 Hp VFD and a 2 hp motor drawing 8 amps and a 1Hp drawing 4 amps. When you swap over you need to change the motor load parameter to match. Depending on the VFD there may be other functions to change as well.

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