Can new activities be added to BPMN editor ++

[krishiyer1969]

I want to do the following things,

1. Add custom activities to the existing BPMN activity list in the BPMN example with their own used specified properties
2. Be able to specify complex data types + global variables that can participate in the

Can this be done in the current framework or does the code need to be extended.
If the code needs to be extended then is drawio an opensource ?

thanks in advance