Hi KenMax
No. Installed apps can not be switched to develop mode since in this mode is everything running locally on the device, where agent is installed.
So what you have to do is to create your own app. You can start with the "template" app (that also live and detect app). Go to the apps from the left panel a and create new "video stream". Then you should see it in the develop menu when installing new app.
You can also download the source code for our apps. Links are in the docs (https://docs.luxonis.com/cloud/perception-apps/examples/). When a new app is created you can upload source code as single zip file (zip the content of the folder, not the folder itself). Delete the existing source and uplodad the zip archive. The you can install it in develop mode.
When you are finished with developing, you can publish the app from the VS code. It will build the app and it can be installed in "run" mode.