Toggle "Use Fixed Frame Rate" via Blueprint possible at runtime?

Is there any way to enable/disable the “Use Fixed Frame Rate”-Option from the Project-Settings via Blueprint or in a similar/other way at runtime?

There’s this node in Game User Settings called Set Frame Rate Limit. That might be what you’re looking for?

Unfortunately not. The behaviour of Set Frame Rate Limit and Use Fixed Frame Rate is different. For Use Fixed Frame Rate i am expecting a certain behaviour of my game at runtime as for setting the Set Frame Rate Lmit.

It should be a boolean value to be set/unset. Here is a screenshot from the area of the Project-Setting:

I just need this one value to be set/unset at runtime but couldn’t find any clues yet on how to do so.

Edit: Even though I assume it is not possible to be set at runtime, I hope to get an explanation on why it does not.