Applies to: Red Range interfaces, RedNet PCIeNX, RedNet TNX

Mac
Yes - For this, you must be using a Mac using macOS Monterey or newer with RedNet Control 2.18.0 installed
To combine units, each device must be daisy cdaisy-chained over Thunderbolt to the next unit 

Windows
No - Due to how Thunderbolt works on Windows, driver aggregation is not supported. And RedNet Control will only work with one interface at a time and the devices will be seen separately by your system rather than being aggregated.

The dual Thunderbolt ports on the Red Range are intended for adding other Thunderbolt peripherals to the chain (such a hard drives/displays) rather than adding additional Focusrite interfaces.