I´m trying to blend the lower body of an animation sequence and the upper body of another animation sequence together to play at the same time, is that possible?

That’s kind of moving the goalposts. The answer to your question was Anim Montages.

Anyway… There is an IsInAir boolean in your Anim BP that is checked every Tick. You can start a timer when it is true, and was false in the previous frame (use a second boolean WasInAirInLastFrame to store this information). After 2 seconds have elapsed, if IsInAir has always been true in that time, you can enable the Ground Pound with a third ICanGroundPound boolean, either in your Anim BP or Play Animation/Composite in the Character BP (and if you choose the second option, I usually have to reconnect the Controller afterwards, or it will “Disconnect”). Finally, if IsInAir is ever false in that 2 second window, reset everything.
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