As "EdH" said before, in fact stacks do not really exist, they are just a label given to a group of notebooks. In that sense the sharing of a stack is already a bulk sharing arrangement, albeit an unwieldy one. The only way out of this problem is to make stacks real, that is make them an existing entity at file & folder level, and make notebooks sit in a multi-level hierarchy. What we need is a nested hierarchical structure, much like the pages in a wiki (look at Atlasssian Confluence, for example). And then make sure that properties are inherited down, with the possibility to set different (sharing) properties for wherever in the structure you are. For example in a specific branch until say level 2 read/write for all and then down from level 3 only a limited group, or only read but not write, and down from yet another level only the owner - you get the idea.