I cannot tell if you are joking or not, but needing to place an entity into the world for a single frame to accomplish this rather than simply applying an impulse to the player is precisely the kind of over-complication I'm referring to
Without having read any of the Unreal Engine movement code, there's a complication here, and that is that "jump" might be influenced by the floor that the player is standing on. The force impulse might be related to the slope in some way. You have to figure out what "double jump" means in the context of there being no floor.
Placing a floor that has the influences you want under the player is, in a sense, a hack, but not an entirely misguided one. A better design might be not relying on whatever the "jump" button does, but writing your own, e.g. applying an impulse to the player directly.
If this sounds like semantics, consider a game like Super Mario Galaxy, which has spherical worlds. How do you determine the correct impulse for which way a "jump" goes? This is where these sorts of complications come from.
I think that captures an issue I have with engines like UE4 which I am trying to describe: it has to support virtually every type of game, so even things which could be relatively simple gain complexity because the engine has to cover cases which may be entirely irrelevant to the project I am working on.