It is my understanding that in order to make a notification from persistent (sticky) to ordinary, the persistent one must be destroyed and a fresh ordinary one must be created.

Regardless, whether my claim is valid or not, you can opt to hide a particular notification from an app rather than choosing to nuke all of them from App details under Settings. NotifyClean (free, donate) can do that for you.

(Note: Android must be rooted and Xposed Framework should be installed)

Instructions

1. When that persistent or troublesome notification is in the Notification drawer, either do

   
   
   
   
   
   • long-press → NotifyClean, or
   
   
   • launch NotifyClean → select the app owning the notification
   
   



2. Select the particular notification you don't want to see. The background will change for that entry and the notification would vanish from the drawer.

   
   
   

   _{(I've not confirmed whether the method of operation of NotifyClean is similar to what Android does when Show notifications is unchecked in App details.)}

It must be noted that you wouldn't be able to see that same notification again in the future, unless you disable the NotifyClean module or uninstall this app or revert the changes inside NotifyClean.