I like the categories module in BS but I noted one problem that can be embarrassing. When I use a parent-child relationship, in BS the requested relationship appear in a tree-like structure, e.g.
However, this relationship seem to be stored in BS with two separate categories, separated by semicolons, e.g. "toxicology; methanol". Thus, when I want to enter methanol as a separate category or as a child category under another (parent) category, a warning appears that it already exists. I do not know how categories behave when exported but I suppose from this feature that they are listed independently from the fact that some categories are in parent-child relationship with each other. I would prefer a tight binding between the parent and child categories which also would allow entering identical category names if they are under different parents.