You can export an app via the following steps:
NOTE: Once the preview is over, you will be required to have a PowerApps Plan 2 trial or PowerApps Plan 2 paid license in order to access the packaging feature. With packaging, you will be able to export an app as a package and import it into another environment. The preview of packaging is now available on. msapp files from your DEV/UAT environment and re-saving the apps in your production environment from PowerApps Studio. We’re very happy to announce that you no longer have to manually move your apps by locally saving.