If you would like to add some company-specific Holidays to several staff and have them added automatically in the People Planner, make sure to add the "Custom Holiday" when creating a new public holidays group.
If you need to do for different teams, simply create a new public holiday group and only assign those team members to it.
Adding People to Holiday Groups
From the Public Holidays page, click on the 3-dot menu and select Edit People
Click Add People
Search for the people you wish to add and click Add Selected
All future public and custom holidays for that holiday group will get automatically added to the people's schedules.
If these people previously belonged to another Holiday Group (perhaps the group with just Public Holidays), they will be removed from the old Group and the holidays will not duplicate.