My original intent was to use an Excel Sheet column to define two different node types, and select a different template for each node type.
But yEd does not allow that directly.
So I had to do this workaround:
Step-1: Add an extra label to the nodes,
Step-2: Use the Custom Properties dialog to insert the node type text in that label.
Step-3: Use "Select elements" command to select all nodes where my additional label identifies a particular type of node.
Step-4: Replace the node shape, by right-clicking on a template in the desired palette, and select the Apply type menu option.
yEd carries out the first three steps, but fails at the last step silently: There is no error message. (Note that I was trying to replace with a custom node from my custom palette.)
Then I simly select a node manually, and then used the context menu from my custom palette. This too does not work.
But I tried to select a standard node from a built-in palette (e.g. BPMN), and it worked.
Conclusion: I cannot use "Apply type" context menu command for a customized node.
Also see- https://yed.yworks.com/support/qa/13656/easy-way-to-change-node-shape
Apparently only shape type nodes allow this trick. But I have used the Entity nodes (from the ER diagram palette), and created four customized nodes.