Unfortunately, FP+ doesn't work that way...
Soarin', Test Track and Frozen are all tier 1 choices. You can only choose one experience from tier 1.
After your initial 3 FP+ are used, you can only add one FP+ at a time. You can't add 3 more at once when you've already used your 3 initial choices.
You can add a 4th FP+ as soon as you scan your MagicBand and redeem the 3rd. You can do this using the
MDE app and the 4th FP+ can be for an attraction in any park that still has FP+ availability. No need to wait until you hop to the next park to secure additional FP+.
Hope this helps clarify things a bit.