Current implementation supports only one artifact upload per step.
Jobs can produce multiple artifacts (mine produces up to 6 packages (3 for release build and and 3 for debug build)
Multiple artifacts upload is currently impossible as the artifact path field takes only a path to a file and does not support wildcards. Of course One could create one step per artifact put it is not a viable option when the jobs number grows.
Taking example on the artifactory upload plugin can be useful as their choices for this task are very flexible and efficient.