Now official:

This is vague enough to leave me wondering if this is Assistant to the GM, like Jason Spezza was or Assistant GM.

We'll find out in time, but I assume it's the first thing. You can read some details about Shane Doan's post-hockey career here:

Shane Doan to the Leafs?
It all began with Nick Kypreos who is quoted as saying that there are “rumblings” that the Leafs are interested in Shane Doan. On Monday’s Jeff Marek show, Elliotte Friedman said that it can’t be confirmed to be happening, but Kypreos was not wrong in what he said.