Native Export with custom Schema

Describe the issue or problem
I have some plugins that add some data to Publication and Issue Schema. I expected to have this exported when using native XML export, but it is not.

So it is desired by design or nobody worried about it before?

Assuming it is by design, should/can my plugins work to interfere in this export/import process to add the custom data?

Is there any other easier/better way of exporting my Issue contents (with publications) to another OJS installation?

My goal is to send the Issue content from production environment to staging, for development/testing purposes…