Compare 2 locations and sync to a third?

[bigjohnsull]

I'm using FreeFileSync as a backup solution to sync files from one drive to another. Unfortunately, my backup drive (E:) is smaller than my storage drive (D:), so I've had to add a second backup drive (F:).

Is it possible to use FreeFileSync to compare D: to E: and then sync anything from D: that isn't already backed up on E: to the second backup drive, F:?

[Zenju]

You can manually copy to a third location using "Ctrl+T" on the main grid.