I am one of those guys that has built my settlers a mansion with a fully-stocked kitchen, games room, and hospital bay.
The problem is, stacking shelves and aligning objects is huge pain. Sometimes I'll pick something up (holding E) and I'll be able to rotate it (using LMB/RMB) on it's Y axis, sometimes on it's X, and sometimes a mixture of the two. It seems to depends on what starting orientation the object has when picked up as to which axis it rotates on.
I would like to know if there is any way (button or otherwise) to switch rotation axis modes whilst manipulating an object. I have looked in the controls and all the settings and can't see anything that affects this.