Yea, Ralf only shows some simple editing there, but it gives a good overview of the process needed to manipulate hatch styles. But you can do any operation you want when editing them, including scaling them using the :CC2SCALE: command.

But yea, bitmaps are much easier to deal with.

The technique Ralf showed here unfortunately only works with bitmap fills. This covers most maps, but some maps, especially maps using line-work (like the landform maps) use different techniques for the fills.

It gets a bit more complicated to scale these. I am pretty sure Ralf showed that off in a video at some time too, but I don't remember which off the top of my head. I'll see if I can find a link for a video or something else, unless someone bets me to it.

If you try with for example the Mike Schley overland style, you'll find that this trick works the way Ralf showed it if you use it on a bitmap-filled polygon, like farmland for example.

edit: Ralf demonstrating editing hatch styles in here: https://www.youtube.com/live/-zZGWKT2pN4?si=LOm5YLc6CtJAds-j&t=1187

If you look at the prompt while using a mirrored polygon drawing tool, you'll notice that it offers you to hold down the control key to create smooth nodes. This allow you to create a plan that has both curves and straights in the same poly.

As Wyvern says, you can add pretty much what you want. The idea behind this project is that everyone can bring their own ideas to the table. A local map should obviously be consistent with the regional map it is taken from, but the general idea is to make it interesting by adding features and locations that wouldn't have been mapped at the greater zoom of the parent map. The marked city locations on the parent map are naturally going to be the largest cities in the region, but as you drill down to more close-up maps, smaller cities and other interesting locations will naturally start to appear. So make it yours, add your own lore to the area (if you want to), and make it an interesting place for subsequent mappers to pick for their maps.

Maybe not exactly the way you describe, but you can add large amount of text to your map using map notes. These don't display in-map, but in a separate window, but you can make hotspots to click to show the note you want, and each map note can have up to 8000 characters. Not quite unlimited, but room for quite a bit of text.

I do this frequently for atlas maps, for example, try downloading and opening the Southern Scar map from the atlas, and hit the Description link in the sidebar, and you'll see a description of the map appear. This is a standard hotspot that can be placed anywhere in a map.

Some more information in this blog article: