Things like uBlock Origin, or EFF Privacy Badger allow this pinning pretty easily so you can see it working. Found the secret because it differs from simply "managing" the extension.
After installing duckduckgo extension, move off the extension page to something else in another tab perhaps.
Click on the Firefox Extension icon in the upper right.
When the duckduckgo rectangular image appears, RIGHT CLICK on it. A left-click won't do. Don't meddle with ... hamburger stuff for pinning purposes.
FINALLY! Yeah, I can manage my extension options, and it would have been handy to have the PIN option there, but no.... When I manage it, I usually just set it to auto-update.
Anyhoo, now that it is pinned, I can click on the duckduckgo extension icon, and see the tracking stuff working. Whew. And I don't run all three extensions mentioned at the same time.
