Add custom activity marker

Hey guys, I’m new to the BPMN world and I have a task where I have to add an activity marker.
What I actually need is to add a plus icon here:

Any help on where to start will be really appreciated

So i know that i need to create a custom popupmenu or better extend the existing one, use as example:

Then I uncommented the getHeaderEntries to generate the example button, but nothing works.

direcotry structure:

this is the content of index.js that returns the custom popupmenu:

This is then this is how called everything in the main index.js



Could you please share a sandbox of what you’ve already done:

We can then help you with that : )