The level of charge would need to be equalized, ie the cells would need to be at the same voltage.
Otherwise a large current may flow upon contact.
You can do this with a 10 ohm resistor.
Once connected in parallel they will effectively be one large cell.
For regular charging and discharging you would not need to monitor each cell.
If you want to know the health of individual cells you must add a way to disconnect them for testing.