Stacker allows you to preview your app as a specific user. This should help you check that the right permissions are in place, and that you're happy with the appearance of your app for customers, partners or clients.
Entering Preview Mode
You can enter preview mode by clicking on the settings icon in your app's lower menu bar and selecting 'Preview as'.
This will then open a dialog box. Here you can select a user and view your app from their point of view.
To exit Preview mode, click the 'x' in the top right of your app window: