Could you gently scrape the bark off down to cambium layer, and then just wrap a scion to that?

Kind of a "scrape graft"?

It would look like a "side-veneer graft".

Just curious.

Yes, Jade, those ‘grafts’ generally occur in nature. Stocks growing in close proximity will naturally graft (roots too) due to the wearing away of each other’s bark until both cambium layers contact. I found one in a tree I was pruning several years ago, should have saved it for my grafting display material… instead, I hammered them apart to see how it happened

I’m actually planning on making such a graft with a plum pollination project. Difficult to describe (and I’m too lazy to photograph it); I’ve looped a rootstock with a whip & tongue scion shoot (grafted last year) behind – up & through – then tied it across and between the base plum's scaffold limbs... It’s gonna look pretty weird, but was the only way I could come up with to incorporate that shoot with the main tree, as I want it to form a permanent pollinating limb. As it settles into place (fortunately the torque of this wild bend didn’t snap the whip & tongue graft off) I’ll ‘scrape’ between where they meet, wrap, and wait for them to ‘weld together.’

…don’t know of many other applications … but cambium to cambium with support and compatible material is all it takes!

I did what I call a scrape graft during my lunch break today. And it was such an easy way to do it. Just scrape it down, then cut the scion like you would for a whip and tongue, and then I wrapped them together, tied it off, and coated with doc farwells. I'll see how it goes.