Like mentioned, the bike computer doesn't care. That's why you don't see that as an option. It could be in your pocket and you can jog with it or drive down the road with it in your car (MTB people seem to forget to shut it off on their drive home) and it will record the drive too.

The only thing it cares about is any external sensors you may have paired and even that is not big deal and it will ignore any sensors it can't find. An example.. Bike 1 could have a cadence and speed sensor. You slap your computer on bike 2 and go for a ride. You will not get cadence info obviously and your speed info will be based on the GPS signal instead. Next day go back to riding bike 1 and it will just work and you'll be back to getting speed and cadence info from the sensors. You could swap the speed sensor and cadence sensor over to bike 2 and adjust the speed sensor settings in the app for the different wheel circumference on bike 2 and now everything will work on bike 2. I'm sure you could also buy additional sensors and pair both but I've never did that.

I reread what i wrote and it looks more confusing than it had to be, bottom line, you can use it on any amount of bikes with little to no effort.