With an SD card as external storage … you don’t do this at all.
You live with 32GB of phone storage for everything that needs to be in Internal Storage and you are otherwise happy you avoided a real pitfall as is proven in this forum time and again.
As your use case included …
… OsmAnd for instance, while being installed as an App in Internal Storage, lets you set the directory for its additional data (including offline map data), and you can set it to the external SD card, too.
On the downside, an external SD card will not be available to Android’s encryption, as it is not part of the data partition. But there is a possible alternative to that, too.