Need longer arms Jim ?

More importantly, have you managed to resolve the issue?

Yes. Rather than try to explain it, look-up "arrows" in the CC3+ HTML Help file using Search, and have it display the "Double Arrow" entry. For some reason typing "Double arrow" in the search bar comes up with nothing...

You can add arrows at both end of a straight, arced or smooth path/line. As we've noted here before though, depending on what size of arrowhead you need, you may be better off drawing the line, adding filled polygon triangles for the arrowheads, and placing them separately yourself, as the automatic system can show the line extending beyond the arrowhead sometimes.

As I've spent the last 18 months on and off mapping elements of the deep undersea (lightless, yet still intelligent-creature inhabited, parts of the Community Atlas world), I'll be very interested to see how this project develops.

The biggest difficulty I found was the lack of prior examples to draw upon (it's a long-ignored topic even in fantasy RPGs for some reason), though for shallower, sunlit, seas, at least there are things like aerial imaging to draw upon, and there are established real-world mapping styles for the near-coastal seas too (like the Marine Maps CA style).

That's much better!

Still seeing some patches of pale grey in places, but that too might be a Sheet Effect. I have found that if you have a stack of objects on different Sheets above or very near one another, that can start to cause all kinds of weird problems, as the Effects seem to start interacting in completely unexpected ways - inexplicable, very often. Even two different Effects on the same Sheet can create oddities which then go away if you simply move one Effect above the other (sometimes)!

Symbol gaps can be tricky to overcome in these cliffs. You may resolve some by simply adding a few short hand-drawn lines of suitable colour and thickness in the appropriate places. Where you have sets of lines forming a "V" shape, you could add either hand-drawn lines or extra, more broken, cliff-lines, to suggest hanging valleys on the cliff-tops, perhaps.