RDCMan doesn't expose an option for Restricted Admin
This might not be the most optimal place for this request, but it somewhat fits and I can't seem to find anywhere more suitable, plus RDCMan is an official Microsoft tool...
Remote Desktop Connection Manager (RDCMan) doesn't currently seem to expose the RDP Restricted Admin option.
This feature is great for secure remote server administration when you can't use PowerShell remoting - many such cases still exist!
It's probably not a huge task either, the GUI just needs a checkbox for the feature which is already implemented elsewhere.
The RestrictedAdmin parameter is for the server side.
On the client side you have to use the /restrictedadmin switch on MSTSC.
You can enable the Restrict Delegation of credential to remote servers to enable however that breaks the Hyper-V Enhanced Session for privileged access workstations.
Paulo R. O. da Silva commented
You can use GPO to implement RestrictedAdmin parameter.