Does an extension or something exist, that lets me see how many tabs I open in Chrome over the span of a day, hour, week, whatever?
There used do be some kind of built in stats using about:stats, but that does not work any more.
Yes it is possible. But this will start counting only after you install thins Extension.
This will say the number of tabs that are open. https://chrome.google.com/webstore/detail/cacjfndbmpdblhkmamkhmdadnoddgoon?utm_source=chrome-ntp-icon
If you want to know the number of tabs you have opened over a period of time then you may need to install,