The TS_CONTROL_CAPABILITYSET structure is used by the client to advertise control capabilities and is fully described in [T128] section 8.2.10. This capability is only sent from client to server and the server ignores its contents.
file:///C:/ts_dev/TestSuites/MS-RDPBCGR/TestSuite/Src/TD/latest_XMLS_16may/RDPBCGR/ _rfc_ms-rdpbcgr2_1_6_2_1.xml
        public void AddControlCapSet()
        {
            TS_CONTROL_CAPABILITYSET control = new TS_CONTROL_CAPABILITYSET();
            control.capabilitySetType = capabilitySetType_Values.CAPSTYPE_CONTROL;
            control.lengthCapability = (ushort)Marshal.SizeOf(control);
            control.controlFlags = 0;
            control.remoteDetachFlag = 0;
            control.controlInterest = 2;
            control.detachInterest = 2;

            m_arrCapSet.Add(control);
        }