SUMMARY
When I click the sound widget, it's possible to change the (audio) volumes of applications that are currently playing audio, but oftentimes one wants to change the volume of an application *before* it starts playing, which is not possible to do, even if the application already has a configured non-default audio setting.

Would be nice if there could be a checkbox or similar in the sound widget pop-up to show all applications and adjust the volume without having them playing sound.

STEPS TO REPRODUCE
1. Put the sound widget on the taskbar.
2. Launch a web browser.
3. Click the sound widget, select the "Applications" tab (default is "Devices").
4. Try to change the volume of the web browser before watching a video.

OBSERVED RESULT
Not possible to adjust the volume until the application starts playing sound, even if it's currently set to a non-default setting.

EXPECTED RESULT
Should be possible to change the volume before an application starts playing sound. Perhaps should keep a list of applications for which the volume has previously been adjusted.

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: 
(available in About System)
KDE Plasma Version: 
KDE Frameworks Version: 
Qt Version: 

ADDITIONAL INFORMATION