How to create a custom shape with include-shape?

[aleksandarsusnjar]

I need to create a shape that is a minor customization of a basic rectangle. I just need to add another rectangle with editable text in its bottom right corner. I am able to create a shape that has the main text editable and act as the basic rectangle but the corner one isn't working. I don't know how to use the include-shape, am not able to find any detailed documentation beyond more questions asked by others, i.e.:

jgraph/drawio-desktop#1439

... or examples of its use online. What I'd like:

Here's what I have presently:

    <shape name="Rectangle with corner note" h="50" w="100" aspect="variable" strokewidth="inherit">
      <connections>
        <constraint x="0" y="0" perimeter="1" />
    
        <constraint x="0.25" y="0" perimeter="1" />
        <constraint x="0.5" y="0" perimeter="1" />
        <constraint x="0.75" y="0" perimeter="1" />
    
        <constraint x="1" y="0" perimeter="1" />
    
        <constraint x="0" y="0.25" perimeter="1" />
        <constraint x="0" y="0.5" perimeter="1" />
        <constraint x="0" y="0.75" perimeter="1" />
    
        <constraint x="1" y="0.25" perimeter="1" />
        <constraint x="1" y="0.5" perimeter="1" />
        <constraint x="1" y="0.75" perimeter="1" />
    
        <constraint x="0" y="1" perimeter="1" />
        <constraint x="0" y="1" perimeter="1" />
        <constraint x="0" y="1" perimeter="1" />
    
        <constraint x="0.25" y="1" perimeter="1" />
        <constraint x="0.5" y="1" perimeter="1" />
        <constraint x="0.75" y="1" perimeter="1" />
    
        <constraint x="1" y="1" perimeter="1" />
      </connections>
      <background>
        <rect x="0" y="0" w="100" h="50" />
      </background>
      <foreground>
        <fillstroke />
        <rect x="0" y="0" w="100" h="50" />
        <include-shape name="Rectangle" x="70" y="37.5" w="30" h="12.5"/>
        <stroke />
      </foreground>
    </shape>

Does anyone have any idea(s) how to approach this? Maybe not include-shape but something else? Maybe the name of include-shape needs to be different (I also tried mxRectangle and rectangle).

[aleksandarsusnjar]

Created an issue from this: jgraph/drawio-desktop#1806