How to "link" two nodes?

I’ve noticed when looking at some fonts that the S often has two nodes on a path across the length of the diagonal. These nodes appear to be linked in some way. When I drag one around, it doesn’t behave like a normal node and the path extends in a direct line to the other “linked” node. They are both curve nodes but the line between them is always straight. I have a short clip of the behavior here.

How can I get nodes to behave in this way? I’ve searched the forum and manual and can’t seem to find any mention of this behavior.

Those are smooth nodes. You change that by double clicking on the node or select it and press enter.

Thanks for the reply, Georg. Yes, I realized they were smooth nodes but they don’t act like any smooth node I was familiar with. However, I just figured out how to replicate the behavior. By deleting the anchor points between the two nodes, they automatically become blue square “corner” nodes. If I then convert those nodes back to smooth nodes by selecting them and hitting enter, they both become smooth nodes without the anchor points between them.

A smooth node can represent a curve, as you were previously used to (with an off-curve node on either side), or a tangent (which is what you were seeing here, staying in alignment with the other on-curve and off-curve nodes). fyi.