perhaps that I miss what you're really looking for, but it seams that this feature is already present.
hit ctrl + shift + F (replace Ctrl by Cmd on Mac)... then from this dialog, you can search on current document or, selected documents, or open documents, or the entire web site... for a string, in code, or text, or in a specific tag and don't forget the filter (martini icon on the top right of the dialog)...
Thank you so much... you are great. I have asked the same question to adobe support chat system and but they said that is no option to search entire project and you gave the solution... amazing.
Thank you so much and really appreciate you.
I'm glad it could have helped you. I wasn't sure I understood the question correctly.