My Brave sync does not have the "I have sync code" option

As shown in the screenshots below, I don’t have the option to add a new sync code. I only have the manage synced devices option. This is the same on my mobile browser as well. As such, I’m not able to add any new device to my synced devices

The I have a Sync code option appears on the device you’re adding (it’s as if saying to the new device “I’ll be using a code from a device already on my Sync chain to add this device to the chain”).

So when you go to add a new device to the chain (that is, the device is not already on a chain), you’ll see this option:

Select I have a Sync code here. On your other device that is already on the chain (as shown in your second screenshot), select View Sync Code and use this code to add the new device.