You need to work on a project drawing outside of a project in any of the following cases:
When you are working with a project drawing outside of a project, you can use the drawing’s standard styles and display settings, but they cannot be updated with changes that are made to the project standards during that time. So it is important to synchronize the drawing after it has been re-integrated into the project.
If you have made changes to standard styles and display settings in the project drawing during working outside the project, a new version of the styles and display settings is created automatically to track the changes when synchronizing the drawing with the project standards. You can select to either overwrite the new version with the current version from the project standards, or you can update the project standards with the version from the project drawing.