Hi,
It is supported to split RDS CALs, and migrate part of RDS CALs to another RD Licensing server.
If there are multi RDS CALs packs on your existing server, you can consider of Migrate your Remote Desktop Services Client Access Licenses (RDS CALs):
https://learn.microsoft.com/en-us/windows-server/remote/remote-desktop-services/migrate-rds-cals
If you want to split existing RDS CAL, one pack, half on one server and half on another server, you can rebuld current RD Licensing databased, then, re-install RDS CALs on both licensing server, with appropriate CALs number entered.
Rebuild the RD Licensing Database:
https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2008-R2-and-2008/dd851428(v%3dws.11)
Also, you can contact Clearinghouse with your license agreement numbers and explain to them about the details. They will help you install them based on your requirement - Locate the Microsoft Clearinghouse Telephone Number for Your Country or Region:
https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2008-R2-and-2008/cc754874(v=ws.11)
Hope this helps and please help to accept as Answer if the response is useful.
Best Regards,
Carl