Hi Marcin,
So since you have it set up as a Montage you could call GetActiveInstanceForMontage and then call SetPosition on the FAnimMontageInstance that it returns. It’s a little clunky but it should work ok.
An alternative solution would be to drop the montage and use an Anim Evaluator node. These are made by adding the animation sequence to the graph as a standard sequence node, right clicking on it and selecting “Convert to single frame animation” This then gives you an evaluator node with an “Explicit Time” pin which allows you to control exactly what time the animation will be evaluated at each frame.
Hopefully that is helpful to you. Let us know if you have any further questions/issues!
Martin