[Marcin Fischer]

I think there is a turnaround to make it work with expressions:
Make two duplicate layers – one with Frame Blending turned on and the other without it (on top of the first one).
Write expression switching the Opacity of the first layer to 0% whenever Frame Rate goes below certain value.

[Marcin Fischer]

Hi, I read this thread with great interest since I have a similar problem.
Unfortunately my problem was not solved here.

What if I want to control the position of JUST ONE of the keyframes by the slider?
The method you provide allows to offset the whole movement (in all or chosen dimensions).
I would like to offset just a certain keyframe. Is that possible with expressions?

In other words:
I want an object to move from position A [X1, Y1] to position B [X2, Y2].
Both points are keyframed.
Than I would like a slider to control the offset of the position B.
So my object moves from position A [X1, Y1] to modified position B [X2 + OffsetX, Y2 + OffsetY].

Is it possible to address SPECIFIC keyframe by expression, so it acts as if it was in different position (while obviously maintaining smooth transition between keyframes)?