FWIW I have created the sections and IDs of 10-19 area that are needed for the family members for whom it makes sense beneath their ID in 11. For example “11.41 The best partner of all” could contain the whole 11 subtree except for the 11.40 part. Or maybe just the 11.20s and 11.30s.
I’m still not sure if I’ll keep it but so far it is easy to find things because the IDs are the same, just their “parent” changes (directory, ring binder).