NGA has a Group Ownership Tool for download and use in your own 10.5 / 10.5.1 Portal. But the Group Ownership Tools are not compatible with the IIS Web Adaptor. The Group Ownership Tools only work with the Tomcat Web Adaptor. Are there plans to incorporate this functionality in future Portal for ArcGIS releases?
The Group Ownership App is a stand alone application that can be installed on your own ArcGIS 10.5 / 10.5.1 portals. It allows users to assert ownership over content shared to groups with co-ownership enabled, and allows group owners to manager (enable or disable) co-ownership for groups which they own.
The Group Ownership App consist of the Update Owners and Administer Groups tools.
•The Update Owners tool is available to all users and allows group members to take ownership over any item, when that group has co-ownership enabled. This allows you to assert ownership over items in the co-owner enabled group, and as the new owner the item is placed in My Content where you can then make edits, move, share, and manage the item.
•Using the Administer Groups tool, group owners can manage (enable or disable) group co-ownership for groups which they own. Only groups where co-ownership is enabled can allow members of the group to assert ownership over items shared within the group. Group owners can also manage co-ownership on the group details page.