It would be useful to have a basic DG node type with no attributes or behavior.
Scripts could use this to store arbitrary data, for things like settings that should be saved to the scene.
Another use came up recently here, where you want an empty node to just hold a rig attribute: https://forums.autodesk.com/t5/maya-programming/does-a-math-round-or-floor-node-exist-in-maya/m-p/89...
Using existing nodes isn't great, because they all have existing semantics and attributes. Using a dummy multiplyDivide is confusing, since it has nothing to do with the multiplyDivide node. Empty transforms aren't appropriate either (clutters the scene with DAG nodes), and they also have a ton of unneeded attributes. https://forum.highend3d.com/t/creating-a-empty-node/6428 suggests using an unknown node, which I think is a bad idea as well, since the existence of unknown nodes in a scene indicates that there are missing plugins.
I've used a custom node for this, but usually adding a plugin dependency for this isn't wanted (that's worse than repurposing an existing node).
A simple node type named "node" with no extra attributes would be a simple solution. It might have a single "nodeType" string attribute, for scripts to identify their node to find it later (usually I add an attribute for this, but it would standardize identifying the nodes, could be used by the node editor for display, etc).
