Lists have three visibility settings: Everyone (visible to the whole organization), Only me (private), and Specific people... (shared with named teammates). This article covers how to set or change visibility and how to choose which teammates can see the list.
When saving a new list
Open the contact table and apply any filters you want.
Click Save As in the toolbar.
Give the list a name and choose List or Saved search.
In the Visibility dropdown, select Specific people...
A Share with checklist appears showing every member of your organization. Check the teammates you want to grant access to. You cannot uncheck yourself; you are always included.
Click Save.
Only the teammates you checked, plus you, will be able to view and use the list.
Changing visibility on an existing list
Go to your saved lists.
Open the action menu for the list you want to change (the three-dot or row-action menu).
In the edit dialog, find the Visibility dropdown and select Specific people...
The Share with checklist loads your current shares and all organization members. Check or uncheck teammates as needed. You cannot remove yourself.
Save the changes.
Switching an existing list from Specific people... to Everyone or Only me removes all per-person share records. Switching back to Specific people... starts with a fresh selection.
What shared teammates can do
Teammates you share a list with can view and use the list the same way they would any org-visible list: dial through it, export it, or target it in a campaign. They can also rename it or change its visibility through the same edit dialog.