Any way to add node to center of canvas?

Sorry if I'm missing something obvious, but as near as I can tell, the point of insertion for nodes is wandering all over the place. I just want a reliable way to add nodes to the center of any given canvas, and have them rearrange accordingly afterwards.

Is there a way to do this?

No files, tests, or entry points are named. Start by locating the node-insertion and canvas-layout entry points, then determine how a caller could specify a canvas center and how rearrangement is triggered; done means nodes can be added reliably at the chosen canvas center and the resulting layout is rearranged as requested.

Written by the indexing model from the issue text.