[UMAP] Linking public data to custom markers or surfaces hosted in private UMAP instance

Hello dear mappers,

I'm currently working for a public administration (30K citizen City) that is considering using OSM as a open-data backend for all publicly available content that we would also heavily enriched with our own data. Nevertheless, we'd prefer to keep technical informations or sensitive content in a private instance of UMAP.

Therefore, I'm looking for a convenient way to link custom and "private" information (that would be kept in our own UMAP instance) to POI or buildings that are publicly available on the OSM map.

For example, we'd first contribute the location and details of the trash bins that are missing on the public map. Afterwards, we'd like to link them to our own pick-up circuit, designed and updated in UMAP, that is of little interest for the public community.

We'd also like to highlight some paths / road to trace the location of our optical fibers.

The following § have been answered below.

In the same approach, we'd like to be able to rapidly highlight all the buildings owned by the city (the Town Hall, the Swimming Pool) **without** having to create new polygons on top of the existing buildings.

A possible solution that I thought of would be to add specific tags to these building in the public map (Owner="City of ###") before being able to highlight these building in a custom rendering of tiles or using OverpassTurbo.

I'm not sure whether it is possible or compliant with the good practices.

Thanks a lot for your feedback and explanations. I'm still pretty new to OSM but quite knowledgeable regarding community-driven libre projects.