Grouping favorites according to multiple categories/tags

I recently started to use Nextcloud Maps to organize photographic locations. I'm creating favorites to mark places to photograph. I'm trying to use the category to categorize places so I can quickly find places that have something in common. However, more often than not a single place fits multiple categories.

Example use case

• I find an interesting group of deciduous trees that I would like to photograph during fog and during autumn.
• I find an interesting pine that I would like to photograph in winter during sunset.
• I find an interesting corner in a city that I think would look great in foggy conditions.

The categories (or tags, whatever you want to call it) could be "fog", "autumn", "winter", "trees", "city". The first one would fit "trees", "autumn" and "fog". The second one "trees", "winter". Third one "city", "fog".

What I would like to achieve is to be able to filter eg. everything that's marked "fog" because the forecast predicts foggy morning. Or when the autumn comes, I would like to filter everything that I want to photograph in autumn.

Some ideas:

• make it possible to assign multiple categories at once. The problem – how to color the favorite. Maybe have a single "main category" that will be used for coloring. It might just be the first selected category
• add a new field "tags" that is orthogonal to category. Filtering can be done against any tag, I'm thinking something like a tag cloud.

No files, tests, or entry points are mentioned. Start by examining how favorites currently store categories and how category filtering works; done means favorites can be assigned multiple tags or categories and filtered by any selected tag, with a defined approach for displaying their color.