Proposal for visualizing which nodes will be offset into which direction:
Draw arrows on links which will be offset:
Issues with that:
- These arrows are already used between reroutes, so they might already be drawn. This could for example be resolved by drawing them differently (different color, different size, etc), or by hiding arrows while transform.
- Tight node layouts - there might not be enough space for drawing the arrow.
- Zoomed out view - arrows are drawn quite small then
- Draw nodes or links that will be offset in a different color or with a slight different drawing (note that I'm not a fan of using color only to visualize such things, I guess we have many color blind users)
- Draw arrow icons or similiar, like here (could also be an overlay)
The arrows are nice but might be too subtle and collide with the rerout arrows you mentioned.
Outlining nodes to be offset with some color or as if they were selected could be more visible and also more explicit since all nodes to be moved would be highlighted as opposed to the icon.
Ideally this could would be done with an actual live preview as one moved the to-be-inserted node around the others would be dynamically offset to their future positions, but that is probably a lot of additional work.
Arrows on links suggest the operation has something to do with links - it does not, it moves the nodes.
Here is a mockup for you. The nodes that will be moved are indicated by a slight highlight:
The highlight can be done in numerous ways, like an outline for instance.