Glad that additionalStrings_ worked for you and that is the method that I would recommend if you really need them in that format.
Because the simulation runs the same way whether you have two equipment schedules or one equipment schedule that is effectively the sum of two schedules, this situation is an edge case that only affects people who plan to work with the IDF in text editors after it is exported from Honeybee. For this reason, I can’t see us implementing support for this in a way that affects all of the non-edge cases for which Honeybee is used. So support for this is likely to be limited to OpenStudio measures and additionalStrings for the time being. Or, if you can think of any other ways of implementing it that do not affect the existing workflows, we can consider that idea.