The hopTo app allows you to view your content in multiple tabs.
upon opening the app you are presented with the home tab as the single tab open.
tapping the "Add" button on the top right of the app opens a new tab also as a home tab. Note in the image below two open 'home' tabs. Once there is more than one tab open it is also optional to close one of them by tapping the X button that is now available to the right of each tab's name.
You can open files in any of the tabs you have open and work on multiple files. Opening a new tab is also available by opening a file directly into a new tab by using the orbit menu. You can read more about it in the following link: Open a file into a new tab using the orbit menu
There is a maximum limit of 5 concurrently open tabs. When you reach that limit the "Add" button is no longer available to open new tabs. Trying to open a new file in a new tab using the orbit menu will result in an error stating that the maximum tab limit has been reached.