There are a few ways to control volume between apps in Windows 11. The first way is to use the volume mixer. To do this, go to the sound icon in the bottom right corner of your screen and click on it. This will bring up the volume mixer. From here, you can adjust the volume of each individual app.
Another way to control volume between apps is to use keyboard shortcuts. To do this, press the Windows key + I to open the Settings app. Then, click on the "System" category and select "Sound." Under the "Output" section, you can choose a keyboard shortcut to adjust the volume of all apps.
If you're using headphones or speakers, you can also use the physical volume buttons to adjust the volume of all apps.