In Projects --> Collaboration tab --> Action Item, auto-suggest is not working for ‘Assign To’ filter. We could see that this ‘Assign to’ browse uses ‘Project Resource Associations’ lookup which retrieves only the resources from the project. Even though, the ‘Auto-Suggest’ option has been enabled for this lookup, it does not work as expected.
The ‘Assign to’ in Action Item in Organizer works as expected which uses ‘Active and Locked Resources’ lookup.
I am not sure if we are missing anything in the analysis, please let us know if there is any work around for this.