Seen this before, so you have to assume the possibility.
Can Multiple Circuits Share A Junction Box? (Find It Now!) – PortablePowerGuides
But if you want a single box to accommodate multiple circuits, the size is your only limitation. You can use as many circuits as you want if the box is large enough to hold them.
FYI - They do it here in the disconnect box for the air-conditioner where you have 220 v for the AC plus a separate 120 v circuit/outlet on a GFI.
One off my favorite electrical tools.
Klein Tools NCVT-2 Voltage Tester, Non-Contact Dual Range Voltage Tester Pen for Standard and Low Voltage, with 3 m Drop Protection
https://a.co/d/bMEvJ9n