I created this pack of tentacle symbols for use in the Sewer Encounters Live Mapping session by Remy Monsen, in which he explains as part of the show how to create your own new symbols from graphics from outside the Profantasy collection and integrate them into the CC3 system.

The pack contains 9 dungeon scale symbols and can be downloaded here.

Here is an example of the tentacles used in a Winter Trail map.

I'm not sure I know for sure what you want, but I did write a blog a while back about achieving various map effects here:

There is a bit about increasing the contrast (number 3), and if that's not what you meant there are several other effects that might be the one.

There are lots of different things you can do, but possibly the easiest if you happen to have an image of an old piece of parchment is to import that image onto a sheet that has a Blend Mode sheet effect on it set to multiply right at the bottom of the list of sheets (on top of everything else in the map).

I expect lots of others will come along and recommend more ways of doing it that are equally good, but that is one way of doing it within CC3.

It certainly looks like it should be visible.

Can you see the text on your cursor just before you place it? The only other thing I can think is that the text is there but incredibly small. If you think that might be the problem check the size of the font in Text Properties. Sometimes, and for reasons I'm not sure I understand, the text can start off really tiny.

This kind of flaw usually occurs when there are two nodes too close to each other and is more common in these heavily fractalised polygons.

When you say you tried changing the amount of nodes, do you mean you tried SIMPLIFY on the keyboard?