I have published the ability to turn on/off particular Adhan(s). Please update your app to receive it. After you confirm that it is working properly, I will officially release it.
Regarding the volume settings, I am afraid that is not always possible. When the speakers are Google/Nest speakers, unfortunately it is only possible to set the volume when something is playing. Although this means I can set the volume so the Adhan plays at the new volume, I cannot reset the volume back to what it was before. Please see @bravenel's comment in Google Home. Set Volume doesn't appear to be working :
For GH mini, it will only adjust volume while it is playing something. So start a track, or tts, then set volume.
Since I do not have any Alexa devices, I cannot test to see if Alexa has this limitation or not. However, since it affects Google/Nest devices, I think it may be best to avoid this setting if possible in the app itself.
However, there is a way that you can workaround this problem. Please consider setting up a rule with Rule-4.0 - Hubitat Documentation like the following:
The comparison of
Hubitat is required because it is Hubitat itself that plays the Adhan track. This will set the volume of your speaker to be whatever volume you want whenever it plays an Adhan (or anything else from Hubitat).
Sorry for suggesting the workaround solution, but I am hesitant to add a functionality to the app if it might not work for all devices/users. Please let me know if you have more questions, and I will try to help out. Thanks.