There currently is no ability for an Admin to assign security to specific users in Parcel Service. The current workaround is to have users create their own package and to not check the "Public" box, so that way it only appears to them. This is very inefficient and an issue when turnover occurs in the organization. I logged an IdeaStream idea with what I think should be a pretty simple and straightforward forward solution leveraging existing functionality. Take a look at it here and add a comment to increase the attention.
JIRA Ticket: MP3-2311 (onestreamsoftware.com)
Also related on the topic of Parcel Service, it would be really powerful to be able to embed XFGetCell's within the email body of a Parcel Service package. I put that into IdeaStream, too.
Parcel Service Dynamic Email Message - OneStream Community (onestreamsoftware.com)