The external sharing level of a site determines which type of users outside an organization (i. e., guests) may be given access to the contents of a site. 

Yes, you can use one of the Quick Actions to set the external sharing level for one or more OneDrive, SharePoint or Microsoft Teams sites. 

To do so, proceed as below:

1. Navigate to Explore Sites and click the Quick Actions button:
   
   
   
   
2. Select the first option in the wizard: Set External Sharing Level and click Next.
   
   
3. Select your Organization, then choose the external sharing level you wish to apply to your site(s), then click Next.
   The sharing levels are organized hierarchically from least restrictive to most restrictive, and are explained below:
   
   • Only People in your Organization: This is the most restrictive sharing level. It does not allow users outside the Microsoft 365 organization to be given permissions for contents of the affected sites.
   • Existing Guests: This sharing level allows you to give access to guests who are already
     included in the directory.
   • New and Existing Guests: This sharing level additionally allows you to assign permissions to new guests if they authenticate with a Microsoft account or a verification code.
   • Anyone: In addition to the possibilities of the New and Existing Guests sharing level, this sharing level allows guests to access contents of the affected sites with sharing links that do not require any authentication.
     
     
4. Using the checkboxes, select the sites you wish to apply the selected External Sharing level to, then click Apply External Sharing Level to make your changes.
   
   
   
   
5. You will then be shown a summary of the actions performed, click Done to complete the wizard.

Note: All actions will be audit logged and viewable in the Activity Log, along with the details of the user account that performed the action.