If you cannot disable the extension directly in Chrome, the next best option is to tell the SEP desktop client to stop injecting the plugin. This is the "proper" way to do it without hacking Chrome flags.

In this comprehensive guide, we will walk through exactly how to disable or permanently remove the Symantec Endpoint Protection Chrome extension. Because the extension is tied to the underlying SEP client software, there are several different approaches depending on your specific situation. The correct method depends primarily on whether your computer is managed by a company IT department or is your own personal machine, and which version of SEP you are running.

The SEP client runs as a background service with high system privileges. It monitors the state of the Chrome extension and automatically rewrites the ExtensionInstallForcelist registry key whenever it detects that the key has been modified or removed. This is why more aggressive measures (disabling the IPS policy or modifying registry permissions) are necessary for a permanent fix.