While I can live with Chenmunka's suggestion, I still think it's way too early to do so. There is no real gain to separate between various DOS from Apple - wich DOS, Prodos as well as SOS are - GS/OS is a different beast - like GEOS.
By labelling with a too fine granularity tags again become less useful. Right now we have barely passed a dozend questions tagged apple-dos, splitting that up might do more harm than it adds clarity.
Personally I'd wait for passing like 100+ questions (and thereof 30+ specific to ProDos) before turning the generic apple-dos tag covering all DOS type os into a specific for the DOS line.
Not to mention that a apple-prodos should, like an other, only be applied if the question is really related to ProDos, not just because ProDos is somehow mentioned as context.