You should be able to see the setting in 'Secret Settings'. It's between 'About Firefox' and 'Secret Debug Info' at the bottom of your screenshot.
Bug 1866624 Comment 6 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
You should be able to see the setting in 'Secret Settings'. It's between 'About Firefox' and 'Secret Debug Info' at the bottom of your screenshot. Out of an abundance of caution, we have remotely turned off the Firefox Suggest feature, so you should see this flag disabled now. If you see improvements, could you try to then enable it and see if it gets worse again? That would still help us verify that this feature is affecting application performance. Thanks again!