Is there an association for academic managers? I there an international society/association for building a community of academic managers (such as department heads, deans, etc)?

I found Association of University Administrators, but it is for administrators (e.g., directors of offices) rather than academic managers.
The Association of Deans and Directors might fulfill what you are looking for: it is not clear from their website the degree to which it is international, but there also seems to be nothing that indicates it is not.