In simplified terms, the MERGE layer has id 0 internally in the software. What happens if something tries to go to a layer that doesn't exists, it will default to 0. Can be avoided by having the expected layers in the map.

Just for the sanity check, I assume you have tried restarting CC3+, as well as also trying with a new map.

There are situations where a command can "hang", but restarting CC3+ should take care of that. Do you experience similar issues with other toolbars, or just the Source Maps ones?

As for the buttons not having any tools, these tools are connected to the style of your current map. So if you start a new map in say Dungeons of Schley, it is quite natural that the park button doesn't have any tools, because there are no tool sin that style named "Park". These buttons are actually just filters, that show all the tools belonging to the current style that matches the filter set by the button. The Park button from CIT is unlikely to produce any results with most styles except the SM Cities style map itself since it is a specialized tool made for that style (which is also why the Park button doesn't normally show up, only when you switch to that add-on. It is possible to change your map to fetch tools from another style, but you're unlikely to actually want this as their visual style aren't designed to mesh well with your current map, whatever that might be.

Well, you can still submit it to the competition if you plan to make a regional map later. There are several other participants submitting villages from yet-unfinished regional maps. Nearly a full day until the deadline.

The scale of the rock fill causes it to appear a bit pixelated. You need to change the fill resolutions a bit. Try to go into :CC2RESMODE: and change the fill style resolutions from there, just go in and divide every value by 2.

The premise is actually very much the same as in the video even for a more stylistic approach. The only way to place the perpendicular lines along the main line is by having them as symbols, but they can be very mush simpler than the symbols in the video, basically just a symbol made up from a single line. So I recommend just following the video instructions, just make everything simpler, and skip everything about effects setup, and you probably want to put everything on the same sheet since the separation was only for the sake of the effects.

It should be possible to just put all those commands into a macro that goes into a drawing tool to make a nice tool that then draw everything for you.

Another alternative is also to use a style similar to what is found in the "Annual Modern City" style. This tool is made by combining two lines, one solid, and one slightly narrower dashed line. This is simpler than the above procedure. but might be more stylistic than you want though, depending on the style of your map.