[Dnick]

How do I get threads that I have posted to, to show up in my UserCP?

If you're wanting to see all your posts beginning with the newest first, select TOOLS > Find My Posts from the drop-down menu at the top of the page.

Minor clarification on this point: You will only be able to see your last 500 posts. If you have posted more than that, I'm not sure if there is a way to see older ones than that.
Also FYI, you can see both of those options (see my posts & see my threads) by clicking on the magnifying glass on the right as well (above "log out").

 

[Dnick]

..........

EDIT: I don't see a magnifying glass above "log out" or anywhere else. Do I need a magnifying glass to see it?

Are you using a mobile version? It (mag. glass) might not show up on that.

In any case it's on the black horizontal stripe just below the RL pics, on the extreme right of the page. (on the 'new' version format)
The "Log Out" tag is just below it, underneath the black stripe.

 

[Dnick]

Windows 7 Pro, Chrome and Internet Explorer. There's no magnifying glass here.

That's very interesting. I'm on Windows 7 Pro (SP1), Google Chome (not explorer).

When they first launched this new forum format, the magnifying glass would disappear intermittently from time to time. It was there initially, then went away, then would come back a few days later.
I provided that feedback to the admins (via the thread they set up for that), and eventually, it quit going away. Don't know if the reason you're not seeing it is related, but I am seeing it now, and it has not gone missing for several weeks on my end. I know there were several issues with how some of the "search" functions varied, for instance on mobile platforms.

Just for grins, try going to the bottom of the page (left side) & switching from RidgelineOwnersClub(Full) to RidgelineOwnersClub(Classic), and then back again. See if that effects anything.

 

[Dnick]

...........
Using Windows at work on a small 23-inch display with low resolution, ...........

That put a smile on my face.... we've come so far in the past 20 years. There was a day when a 23" monitor was absolutely HUGE!
And low resolution meant your zeros looked like a ring of 8 or 10 square white boxes linked together... that's if you were even on a raster screen, and not an old green stroker (vector) display.
And no, there was no color.......