Hi Fozzie, welkom to to forum
You can record this in 2 places in your routes and in 1 place in your tracks.
Itineraries:
Open your route, and go to "Route information" via the left dropdown menu.
In the description box you can put all the notes that you mentioned in your post.
Via the same drop-down menu, you can go to "Comments" and you can also leave a comment here, but that is actually more intended for people who have driven your route.
Track logs:
Open the Tracklog, and in the left column, you will also see "Comments", this one is actually intended for people who use your track to leave a comment.
Also take a look in the RouteXpert library and open a route that is there, the 1st text block you see is the text that is in the route information.