When I navigate to Special:Preferences#mw-prefsection-gadgets, I can't see where to disable Reference Tooltips. Thank you for looking into this!
Topic on Talk:Reference Tooltips
What wiki are you on? If you go to MediaWiki:Gadget-ReferenceTooltips on your wiki you will see what label this option has and you should be able to look for that label in your Preferences.
Thank you! I thought that it was a global setting and was trying to change it on MediaWiki to take effect on my enwiki account.
You might also be looking for "Reference Previews", which is a different thing. That can be found under the "Preferences -> Beta Features" tab.