Kerbal Space Program

Expected behavior: when using Offset or Rotate gizmos on parts placed in mirror symmetry, they will respect the mirror plane around which these parts were placed even if the part to which they are attached was moved or rotated.

Observed behavior: when using Offset or Rotate gizmos on parts placed in mirror symmetry, the tool removes the other copy of the part from its original position and assigns it a new position along symmetry plane derived from current orientation of the root part.

Motivation: reported after endless frustration with trying to add plane boosters created in SPH as subassembly to payloads created in VAB. The other, related issue - editor failures to place struts and fuel pipes in mirror symmetry correctly, is I believe already reported somewhere, though the principle is the same.

Reproduction steps:

• enter SPH
• start with command pod, attach the Rockmax HubMax port to it (to add some degree of freedom), then attach e.g. an SRB
• switch to 2x mirror symmetry and install plane wings on the SRB
• rotate the SRB e.g. 30 degrees so that wings are now in slanted plane
• using Offset or Rotate tool, try to adjust one of wings
  Observed: the other wing, instead of shifting or rotating relatively to its placement, skips to new position
• return to original SRB with miror-symmetry wings, rotate it 90 degrees and attach to the side port on the Hub part
• using Offset or Rotate tool, try to adjust one of wings
  Observed: again, the other wing skips to new position and they are now on the same side of the SRB

Both tools should figure out the plane around which the part was placed, e.g. from relative positions of affected parts, and perform the adjustment in symmetry around that plane.

For comparison, both gizmos appear to have no problems working with parts placed in rotational symmetry, even with arbitrary placement of their parent part.