How to filter packets with string pattern matching using Wireshark?

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networking

I am finding a way to filter packets containing a specific string pattern using Wireshark. I found some ways to filter packets by IP address/range, UDP/TCP ports, protocol types, ... I even found a way to find packets among captured ones by string patterns. But my problem now is that how to combine the two functions: filter and find. What I want to do is to filter specific-string packets among captured save as one file. So far, although I can find such packets but I can't filter them. That's, the packets I am not interested in are still there.