The answer is Shift-J. Shift-J. J joins two ways ways, when both ways are selected; shift-J selected and they have compatible tags. Shift-J converts a node shared by several ways into one node into two for each way, when a the node is selected. selected. I should have looked a bit further before posting the question.

The answer is Shift-J. J joins two ways when both are selected; shift-J converts one node into two when a node is selected. I should have looked a bit further before posting the question.