Oracle Visual Builder provides a unified development platform that allows you to build both web applications - accessed from browsers - and mobile applications - installed on devices. The development environment however keeps the development of those two as separate things in Visual Builder. There are several reasons for this including among others the belief that designing a good mobile experience - small device and touch gesture - is different from designing an application that is used on a desktop with a mouse. That being said, the technology, framework, and app structure for both applications is basically the same. So, with a little hacking you can take an app that started as a web app and packages it as a mobile app. This is what the video below shows.
While the core of the application is the same, there are several things we create in the wrapping artifacts of your mobile app that are different from your web app, for example your mobile app gives you a place to specify iOS and Android build configurations as well as PWA options. If you already have a web application in place, instead of manually adding all of these, it is easier to create the mobile app using Visual Builder, and then just copy the flows and pages over.
In the video, I export the web app and then copy the flows and the contained pages over into the directories created for the mobile app. I can then import the modified app back into Visual Builder. As a short-cut you can create identical flow names in the mobile app menu to the one you used in the web menu. Next you'll see that you might need to add some meta-data to your mobile app - such as the pointer to the services.json files you are using for your web services or business objects data sources. Another thing you might want to adopt from the "true" mobile pages in your app are the page template tag and the hamburger menu which you can copy from existing pages over to the migrated pages - check out the HTML code of a mobile page to see them.
Once you got everything looking the way you want it, you can package your app as a mobile app and run it on your device.