Corner spot where three faces meet I tried modeling this with modifiers:



Ideally I want to create only the part on one side and have the other two added by modifiers.

How would you do this? I mirrored it 90 degrees once and then copied the original to the top. Can I apply two separate mirror modifiers on one object, so they don't apply on top of each other? That way I could mirror the original 90 degrees in Z and 90 degrees in Y direction without ending up with four objects.
I would make this with linked duplications that I would join later on, but you could do it with 2 Mirror modifiers:


Create your shape. Put an empty on the axis.
Give your shape a Mirror modifier, choose the empty as Mirror Object.
Rotate the empty 45° on the Z axis.
Create a second empty (perhaps another shape) at the exact same place as the first one.
Give your shape a second Mirror modifier, choose the second empty as Mirror Object.
Rotate the second empty 45° on the Y axis.
You should be right.