You can use the search box on the calendar page to quickly find and navigate to activities by name or #tag:
Activity tags can be captured or assigned from a workout when one is paired with an activity.
If you try and load 13 years worth of data on the calendar page, activity list view or fitness page the app will struggle. That’s a huge amount of stuff to fetch from the server and render. All the activities are sent back via web sockets. I think the buffers on the server fill up before the data can be sent to the browser which is maybe why you managed to get it to work by doing a couple of years at a time. I might be able to fix that but the app will be slow with that many activities.
This isn’t something I have tried to optimise for because its not something people do often 
You can get your all time power curve on the /power page. That is computed server side so is fast.
Anyway let me know how you get on. I haven’t used Today’s Plan much so I can’t give you too many pointers. One thing I did like of theirs was their power vs HR plot. I built a better one (IMO) in Intervals.icu (see /compare page). I managed to get a little fitter in 2023 vs 2022:
It sounds like you might be a software developer? If you know some Javascript you can extend Intervals.icu in many places:
Also checkout the guides: