Transferring data between two PC’s is quite straight forward in GA3 especially if you use the custom backup and custom restore options.

Perform a backup to PC, copy the backup file lastbackup.bak or if you performed a custom backup, then copy that file from your main PC to your secondary PC

Next go into the Admin and choose Backup & Restore Menu followed by restore from custom. Choose the file you copied over and GA3 will import from this.

For instance : You can perform a custom backup directly onto a USB memory stick, choosing the name yourself

Plug the USB stick into your second PC, then from GA3’s admin choose custom restore.
Browse to your USB stick and click on the file you saved above.

If you plan to work on the second PC you MUST NOT also work on the first PC as the data on the first PC will be over-written when you re-import it at a later date.