The macOS Migration Assistant in Applications/Utilities will transfer all your data to another machine. If you want to migrate the data manually, find the correct folder below and copy it to the same place on the new mac.
In case your hard disk or SSD should have a failure, you can restore the data folder using Time Machine or your backup tool. The application (GrandTotal, Timings etc.) needs to be closed first.
Either download and launch this Application or look for it manually as described below.
|GrandTotal 3, 4 & 5||~/Library/Application Support/com.mediaatelier.GrandTotal3|
|GrandTotal 1 & 2||~/Library/Application Support/GrandTotal|