Best is to export one of the projects to a format with a lossless codec.
You are on a Mac, so I would go for QT Animation.
Export / Devices / Custom / Advanced Settings / Quicktime
Animation will be found under video codec.
Import this export into the other project.
If file gets too big you might want to try Prores 422 HQ
Wow thank you for the speedy response! I came home and tried your recommendation, but this doesn't allow you to edit the project anymore. Is there a way to merge projects instead of exporting so that you can continue to edit both projects together in the same project? Thank you in advance!
but this doesn't allow you to edit the project anymore.
That is correct. Elements does not have the ability to import a project into an other project.
Bummer. Thank you so much for your response though!