Impossible to add a second collection

[benoit74]

When I try to add a second collection to an existing title, it fails.

For instance if I try to add "Endless / endless" to "academia.stackexchange.com_en_all", it fails. Looks like a problem with book location unique constraint, but I don't get why.

[kelson42]

Having a title in two collections seems a source of big problems. Does this point have been discussed in detail? Do I just have forgotten?

[benoit74]

Yes it has been discussed, documentation we wrote in the wiki concepts (actually you wrote, with both renaud and I on the call on Dec 4, 2025) says Many Collections can share a single Title.

What are the big problems you see and we've totally missed so far?