You found a manual, but it is not the correct one for your system. If you take a close look at the dash switch, yours is a bit different looking than the one in the manual you have a link to. And that manual is for a TDSE. The picture I have below is what you should have - a TVSS. I'm also showing the dash switch (same as yours) and the remote you should have (same as shown on the TVSS owner's guide). Yes, you should have a remote. I don't believe the functionality will be quite as user friendly without it - if it is even possible to use without the remote. The pictures I have is from a complete spare system - my son's two ST185's have this feature, so I found a spare system in the salvage yard just in case one of his systems acts up.
Some of the technical service bulletins in your link are very valuable, especially the one about programming remotes to the system (that isn't in the user manual). Thanks for including those - I'm making copies for our records - they may come in handy.