I actually solved this exact problem recently (who is NOT trying to recreate Roam Research amirite?) And surprised no one else suggested the solution I came up with: just use a text column? When a new list is created the items get incrementing chars as text. If a user reorders an item, the items new sort order value is the value of the item above it concatenated to an "a". This is infinitely extensible, it's only slightly a drag on storage, and very trivial to clean up with some periodic code if storage is actually getting to e a problem. Works like a charm and Dont need to modify postgres itself for this!