Set rotation on y-axis with angle relative to current position

I have an object and an angle.

I want to set the rotation of the object by the y-axis to my angle.

Like this:

 transform.rotation = Quaternion.Euler(0, angle, 0);

However, I need the rotation to still be relative to the the current rotation.

The sample code will only work if the object is on a plane ground, but let's say it's standing on a wall with the rotation of (0, 0, 270).

The code sample would put it on the plane ground again.

My thoughts are using: transform.Rotate(angle - currentYAngle); or transform.rotation *= Quaternion.Euler(0, angle - currentYAngle, 0);

But I cannot figure out how to get the currentYAngle, because neither transform.rotation.y or transform.localEulerAngles.y returns the value I need.

Can anyone please help to set the rotation of my object by the angle relative to the current rotation?