There is a group policy called Turn off all balloon notifications, but what if you want to turn off only one specific notification?
The taskbar does not offer fine-grained policy control over balloon notifications. All you have is the giant sledgehammer that turns off all of them. If there is a specific balloon you want to disable, you have to check with the specific program that is raising them, or the specific product feature, to see if it offers a way to turn the balloon off.
For example, there is a setting to disable the low disk space checks and another one to disable notifications that tell you when you have lost the connection to a networked file and are working on the local copy.