How to export project files to another project?

to copy a MegaCore function, the easiest way may be to copy the variation .v/.vhd into the new project, open the variation in the MegaWizard, then select the variation, and regenerate the core

alternatively you could gather all of the files named <variation_name>.* and the associated libraries (they should have obvious names like fir_compiler-library) and copy them to the new project directory. add the copied <variation_name>.qip to the new project and you should be good to go (newer .qip files use relative paths)

i use a script to create .qip files for my own HDL to make the process easier