The admin created an app on Qlik Sense and would like to share it with the other users, so that the users be able to edit it ie access the data load editor and the sheets editing without creating duplicates. Is there a way for this?
If I understand your question the answer is No. Each user can duplicate a published app to their work area and make changes there. But if you have multiple people changing the load script at the same time that will be a disaster waiting to happen.
Once an app is published users with rights (based on security) will be able to add new sheets to an existing app. They can't change published sheets. Other users would not be able to see these sheets until the admin publishes them.