I had done some work with a client who had this feature in their project. As far as I can tell digging around through all the editor and project settings, there isn’t a way to enable this feature in the base build of the engine and it was something custom they had built, although it should really just be a standard feature.
It was a godsend in so many situations where I wanted to reorganize my graphs for easier readability and I could drop dozens of reroute pins when working through the graph and then later go back and delete them while all the connections would remain connected correctly as if the pins had never existed.
It was also nice for organizing giant arrays of things as well like box blur offset nodes that have 8 outputs (or even larger custom arrays). When building big the arrays, I could have some ugly and messy batches of pin hierarchies sitting next to each other as a result of duplicating bits and pieces of existing nodes just to get everything connected, and then with one quick delete, remove all the clumped up reroute pins while leaving several dozen connections in tact.
The current behavior is aggravating in larger graphs as removing a reroute pin nukes the entire connection, so you have to slowly drag and trace the connections back to each other to reconnect. It doesn’t even make sense to me from a logical perspective, as my impression is the reroute pins are largely there for visual organization, so removing them shouldn’t be changing functionality of your material but rather removing the visual fluff in the material graph.