Currently, in Desktop and Mobile Notifications, there is no preference that allows me to receive notifications only from contacts assigned to me or unassigned.
The existing options go from Send me notifications for ALL the contacts and mentions to Send me notifications for contacts Assigned to me and mentions.
The problem with these options is that Send me notifications for ALL the contacts and mentions sends me notifications about contact's assign to other users. So it's too noisy in a Space with many Users.
The problem with Send me notifications for contacts Assigned to me and mentions is that doesn't notify me about contact's that are unassigned.
Adding a new notification "Send me notifications for contacts assigned to me or unassigned" can help close that gap.