Extract part of a PCB to make a new footprint in KiCad
Yes, you can export all the footprints used in your PCB file to a .pretty folder.

Go to File > Archive Footprints > Create Library and Archive footprints.

You will be prompted to give a name to the .pretty folder. That is it, you should find all the footprints in the project folder. You can modify the footprints in the footprint editor and also use them in other projects.

This feature is available in the version you are using 4.0.7