rdisp/use_rfc_dest_lookup is a SAP Parameter attribute which is used to control Enable lookup of RFC destination for backward GUI connection information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
If RFC connections can be set up by SAProuter, communication to SAP GUI
(for example, for dialog, SAP automation, or frontend printing) is only
possible for synchronous RFCs. Cancelations occur for asynchronous RFCs
and when creating further sessions. The reason for this is that the
system has to build a new RFC connection to the server where SAP GUI is
logged on but where the necessary connection information (back route) is
missing. An RFC destination can be created for these cases in order to
be able to deliver the necessary information to the system and to store
the information in the gateway options there for creating the
connection. This destination must have the name
<(><<)>DB-SID of the client>@BACK@
and be of type 3 (connection to R/3 system). If parameter
rdisp/use_rfc_dest_lookup has the value ON, then this destination is
used for building a connection, otherwise not at all.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.