Hello,
Jumping into the conversation with an additional method of handling it. I added an ArrowComponent to my character Blueprint below for reference.
In the Graph, I used a FlipFlop like you did but I set the default location of the camera (over the shoulder) prior to starting a Timeline (3 seconds) which is used with the VInterpTo node to blend it smoothly to the new location which is my ArrowComponent (AltCamera).
When F is pressed again, it executes a similar sequence except it uses the Timeline/VInterpTo process to blend down to my DefaultCamera I set before.
Plenty of ways to handle this, this is just another approach. 
Edit: This is just reference, you may need to add a branch to check if the camera is in the process of transitioning already and move up or down depending on the direction it’s currently moving.
Hope this helps,
-W