If you have an app that you would like to surface to end users via a workspace, you can do so through the Pluggable Workspace configs in your compute environment. Similar to how Domino uses the app.sh file to publish your app through the App Publishing feature of your project, running the app.sh file in the start config of the Pluggable Workspace Tools will launch whatever app you have defined in your app.sh as a workspace. In order to set this up you need to add a new config to the Pluggable Workspace Tools, see the example for Shiny below. This can be amended to work with Flask and Dash apps as well.
You can choose whatever image you'd like for the imageUrl or you can delete that field and the workspace option will show up as a white box with the name of the workspace inside. When you go to launch a new app/workspace this is what it looks like.
Once the workspace launches the app will reside where the normal workspace IDE resides and the normal workspace settings and menu bars will remain in place. There is no way to remove these menus for workspaces, so if you don't want those menu bars in your app you will need to publish your app through the regular app publishing feature.