As U know, when a player stands on a slope, the angle of the slope changes depending on which direction the player is facing:
Facing across the slope - angle is horizontal
Facing directly/up down the slope - angle is the full angle of the slope negative/positive
Facing in between - somewhere between horizontal and full angle
So I tried the following projections to align an arrow, always facing forward of the player, with the slope as the player rotates:
And the pitch is correct (yay!). But the yaw is also slightly modified (red arrow) from the playerās forward vector (green arrow), because yaw changes from being projected onto the slope along with pitch.
So letās try to plug the playerās yaw directly into the arrow rotation, like the following:
So now yaw is perfect, but at the certain angles the red arrow sticks into the ground (uphill) or points too high (downhill), showing itās pitch is slightly incorrect because itās based off of the adjusted yaw (i.e. they are out of sync).
The results are about the same using the āGet Slope Degree Anglesā node. Actually, itās bit better though certainly not perfect, and the difference gets worse the steeper the hill is.
So it seems like I can get the correct pitch or yaw, but not both. A lilā help please? 
Thank U great one! 
I love the elegance of it, but Iām not sure why itās not quite working for me.
Iām doing a line trace, not using the character component
Sorry, should have made that clear! 
Thank U! But for some reason, itās giving me the identical result. Iām truly puzzled 
Maybe itās the unusual steepness of the ramp, or the long length of the arrow that makes the difference clearer?
Ah, see what you mean, this should fix it
Yes, oh wonderful wizard, the pitch is perfect but the yaw (red arrow) is also redirected in the new rotation
Iām aiming to keep yaw straight (green arrow).
Lost now, I thought you wanted it level with the ground?..
Absolutely, I really appreciate your input on this. But Iām aiming level with the ground at the same rotation in yaw as the player character.
The thing is, when I use āMake Rotator from ZXā and āReflect Vector on Planeā the pitch is perfect, but yaw is also affectedā¦ which is why the green (forward rotation) and green (reflected rotation) arenāt in line.
If I try to correct this by plugging in the raw yaw directly from the playerā¦ yaw is now perfectā¦ but pitch goes out of sync (being based on the adjusted yaw, not the raw yaw), so the arrow/box wonāt lie flat along the slope reliably.
What are you using for the green arrow? Controller yaw?
Oui, player control rotation or actor rotation without any dynamic pitch.
Can you show the code for the red and green arrows?
Here it isā¦
From a higher angle with an orthographic camera, you can see how the adjusted yaw differs more easily:
When the player faces directly up or across the slope, the arrows match exactly in yawā¦ itās the in-between rotations where the yaw deviation occurs.
Now works 100%, even with the floor check on the character movement componentā¦ U are absolutely phenomenal 
Itās often a matter of fiddling around with different combosā¦
Your first level of āsteep hill telekenesisā is ready 
Thereās a niche indie game title right thereā¦ āSteep Hill Telekinesisā. Imma gonna be a bazillionaire! 