Using multiple arguments in ARCHIVE=

Recently I needed to archive multiple files into 7z archives, so I tried adding button to archive single files into 7z, however neither the "Copy ARCHIVE=single,.7z HERE", nor the "Copy ARCHIVE=.7z,single HERE" functions seem to work.
The first one archives all files into one and the second fails, claiming unsupported operation.
Looking at the documentation, there are no examples of ARCHIVE taking multiple arguments as opposed to ADDTOARCHIVE, so I assume it only supports one argument?
Would it be possible to make it support multiple arguments, or adding a "single" checkbox to ADDTOARCHIVE's dialogue window?
And is there a way to do what I want using a script?

ARCHIVE and HERE are separate arguments. HERE isn't a parameter for the ARCHIVE argument; it's a separate argument in its own right. The docs list the arguments and (if any) their parameters.

ARCHIVE=.7z,single won't work (due to single switching things into a slower method of adding files to archives which the Archives plugin doesn't support), but you can use this as a workaround:

(As a bonus, the workaround is also faster for Zip files, even though it isn't needed for them.)

Oh, I see now. Thanks a bunch!