The Quick Add feature allows you to add multiple Users at once however, not the Externals Users. When adding multiple users, you enter basic user information (such as Last Name, Login Name, and Password) and Web Timesheet creates a profile for each user. You can choose to base each user's more specific information (such as their permissions) on either system defaults or another user profile. Profiles can later be edited on a user-by-user basis or by mass edit feature.

Note: An External User cannot be associated with multiple clients either.