You want to use conditions.

In the first condition, you set the gyro menu to be on and in AVCS mode, with the group set to SNGL. Do not set a switch.

Toggle to the next condition and set the gyro to NORM mode, with group set to SNGL.

Now, you have a switch that will toggle between modes.

If you have more than two conditions, you set the gyro type as how you need them to be, whether AVCS or NORM in those conditions. Just remember to set the group to SNGL>