Descriptors Editor not accepting TC.getParam("param") value. Object identification failing

Hi I'm on 12.50 version.

Using descriptors for identification but it cant find objects. 

1)  Tested TC.getParam("param") and it does work everywhere else. 

2) Manually specifying pram in clear text works.

My conclusion that Descriptor editor does not evaluate string from TC.getParam("param").

Tried both JS and Plain editors. 

Please assist.