currently you have a this tool that allows you to approve sheets
the good news is that starting from June 2018 version , you'll be able to do it with just right clicking on the sheet
so in two weeks or so you'll have a simple solution
The status of the app object:
- Not approved: The app object is not approved because it was added to a published app.
- Approved: The app object is approved because it belonged to the app when the app was published.
Published The status of the app object:
- Not published: The app object is not published to a stream.
- Published: The app object is published to a stream. There are two alternatives: The app object itself has been published from Qlik Sense, or the app that the app object belongs to, has been published.
As Liron mentioned, you can use that extension to approve sheets and you'll be able to do it on June 2018 version.
There is also another way to do that. Get the appid of your app and go to apps folder. Find the app file and copy it to another folder. Change its extension to qvf and import it to your sense enviroment over qmc. With doing that all "not approved" sheets go under the base sheets. You can publish that app and all sheets will be under base sheets.
Hope it helps.