hey guys. Is there a shortcut (or can I assign it) that creates a merge and connect any selected nodes to it like a "merge and connect to selected" or something?

drag from the output pip of one of the selected nodes, and then alt-click to place a merge node.

I did something like this also that really helps with connecting existing nodes. Mine also works for other node types as long as they have enough inputs and you have selected multiple nodes. It will try to connect to all available inputs based on the order of the selected nodes: