thanks for clearing things up.
My boss handles the ISSN registration side of things, so while that is good to know (I do share your reservations regarding multiple ISSNs) it’s not quite my choice. I will pass on the feedback though.
But as I read it, it’s strictly one ISSN per Journal, with the option of opening up multiple journals per installation?
Is there a possibility to interlink the different published Issues between journals on the same installation? So the additional material could be found and accessed from the “base” journals Issue page? Manually adding a link containing the DOI of the additional material would be a workaround, but as the journals are managed by users with not much technical skill, I would rather keep the solution as simple as possible.