lightbox viewer on nextcloud instead of draw.io

[PackElend]

It is possible to make use of the lightbox, which allows making use of the plugins, on nextcloud. Currently, we can do it only on draw.io but we have confidential data, what restricts using draw.io fully. Instead of draw.io/?p=ex&lightbox=1&..., I would like to make it accessible via myNextcloud.com/drawio/.../?p=ex&lightbox=1&..., similar how it is possible with the editor which is available on NC (your app) and draw.io.

Neither the draw.io build documentation nor Embed Diagrams do tell anything about such details. I find some more details on the mxgraph repository, Facebook and YouTube but nothing gives me the slightest clue how you could continue. Only if you check src/main/webapp/js/diagramly/App.js, then you find some hints towards the lightbox functionality.