Now added to the atlas. Thanks for the contribution @Quenten

Maybe Shessar's North Alarius map in Sue's spectrum overland can provide some ideas.

The grid button only controls the drawing aid grid to help you layout the drawing. What you have there is an in-drawing grid, a grid that is intended to be part of the drawing, which usually live on the GRID sheet and can be hidden bust by hiding the sheet (or the HEX/SQUARE GRID layer).

Since what you are looking for are essentially just simple markers, if you don't find what you are looking for elsewhere, you can easily just draw them yourself and define them as a symbol. See page 75 of the user manaul that shows step by step how to make a basic symbol marker like this (Or page 105 of the latest published version of the Tome, if you have that)

Nicely done.

My nitpicking self can't help but notice you stuck with the default straight line bulkheads, while the original drawing uses round shapes. Did you consider trying smooth lines instead of the default straight ones to give a more rounded look?