How Actions Are Ordered in the Salesforce Mobile App Action Bar

The Salesforce Mobile and Lightning Experience Actions section of a page layout and global publisher layout drives which actions appear in the Salesforce mobile app action bar. It also enables you to customize the order of quick actions, productivity actions, and standard and custom buttons that are available as actions.
Available in: both Salesforce Classic (not available in all orgs) and Lightning Experience
Available in: Group, Professional, Enterprise, Performance, Unlimited, Contact Manager, Database.com, and Developer Editions

If you customize the Salesforce Mobile and Lightning Experience Actions section of a layout, the mobile app reflects your customizations.

If you customize the Quick Actions in the Salesforce Classic Publisher section, but not the Salesforce mobile app section, the actions in the mobile app action bar are a combination of those in the Quick Actions in the Salesforce Classic Publisher section plus any standard or custom buttons present on the page layout.

If you customize the Salesforce Mobile and Lightning Experience Actions section, the standard and custom buttons in the buttons section of the page layout aren’t automatically included in the action list. You must add the buttons as actions from the Mobile & Lightning Actions category in the palette.

If neither section is customized, the action bar inherits a default set of actions predefined by Salesforce. The sets of actions differ between objects, based on the most common or typical activities required for each object.