Hi Tahir,
SAP has released SP02 Patch2 for NW DEVELOPER STUDIO 7.50 and it is specified that the issue raised by you is addressed in this patch (Unable to view imported RFCs in NWDS, note 2273877).
Hope it resolves your issue.
Download the latest NDWS from below path: https://service.sap.com/sap/bc/bsp/spn/swdc/notes/default.htm?cvnr=73554900100200001769&support_package=SP002&patch_level=000000
Thanks,
Sandeep B.
