It is not possible to cascade the FireStudio 2626 and an FP10, as the drivers / control panels are not compatible with each other.
For cascading the FireStudio (2626) with other devices, take a look at the User Manual, page 42 available in the download page for the FireStudio 2626 in the discontinued section.
Last version of UC and supported OS was Mac OS X 10.6.8 / Windows 7 SP1 that supported the 2626 is also on that download page.
Some of the devices that the 2626 would cascade with were supported on newer OS, however the 2626 will not appear on any OS other than it's last supported UC version.
For community support for the FireStudio 2626 go to our community forum for legacy devices.