Hi @aditya.shwetank ,
not clear for me how I can help you, if I understood correctly you already use “Find in Files” and “Cross Reference”, but you have found some limitations on “Cross Reference”…so if this the case please report the issues to our Support in your area so they can report them to R&D.
Regarding documentation or video, not sure I have to check…you just need to build the cross reference list first and then enter your variable in the Filter:
I see some information in AS Help: cross references window
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Automation Studio Code could also help: Ever lost track of where a variable is used? You’re not alone. 
You change a variable in one place… but where else does it show up? Manually searching across files can feel like looking for a… | B&R Industrial Automation
Ciao
Valerio