How Can i edit pcap files in wireshark

edit

It's not currently possible. The old GTK+ version had some limited editing capabilities; that might have required building with non-default configuration options. I don't think that code was reimplemented for the Qt version.

WireEdit clainms to be a "Full Stack WYSIWYG Pcap Editor"; it's not free in either the "source available" or "doesn't cost money" sense.

Some other tools that can edit captures are listed on the Wireshark Wiki's Tools page; some just anonymize packets, but others may allow other changes, such as checksum changes, to be made.