I have 4 cubes symmetrically placed at the 4 corners of a plane and I want to move them along the x/y axis outward/inward the center of the plane witch is also the origin of the 4 cubes?
Take one of the cubes symmetrically placed on the plane and mirror it on the x and y axis. Go to the mirror modifier and set the mirror object as the plane (which they will be placed on at the four corners). Now if you go into edit mode you can select the one cube and move it to one corner, and the mirrored cubes will move symmetrically to the other corners. Good luck!
- Select the objects. Right click and choose Set Origin>Origin To Geometry.
- In the pivot point menu set the pivot to Median Point and toggle Only Origins on.
- Scale the objects in the axis that you want to spread them apart.
You may want to snap the cursor to the origin location that the four objects are sharing first, and when you're done scaling the origins, right click>Set Origin>Origin To 3D Cursor to get the origins back where you have them now. Note that if the origins weren't all in the same location like they are now, you could skip the first step. Since they are currently 0 meters apart, scaling the origins has no effect since anything times zero is still zero.