I'm using Portfolio to track resources, and in some cases there are some tickets that group together the work for multiple people, or the best I can say about an issue is that these 4 people are working on this. I would love to be able to have multiple assignees, but in the absence of being able to do that, having a separate multi-user-picker field to track this would be very helpful.

It looks like this isn't supported though, in my experience and in the docs (https://confluence.atlassian.com/jiraportfolioserver/custom-fields-967895171.html):

The following custom field types are supported:

• checkbox
• date picker
• user picker (single user)
• number
• radio button

• label
• single-choice select
• multiple-choice select
• single-line text
• URL (read-only)

I would love for this custom field type to be supported by Portfolio. Even better, if I could "Group by..." this custom field and have it show me all of the items that each user is connected to in that field, even better.