Look for EType in CStuff in the entity record first. That tells you what kind of entity this is. You'll find the ID's in _ESTRUC.H.

My issue from the very brief look I gave that one was that I didn't seem to actually get valid entities at all, just uninitialized memory. Which may be due to a mistake on my side, or perhaps something that needs to be done that I don't know about, there is no documentation about that call.

Attaching doesn't automatically make corners for you. The only thing that modifer does is to ensure the nodes are in the exact same place, so for your road, it would ensure the start node of the new road is at the exact same point as the end node of the existing one. But line endings are perpendicular to the the direction of the line, so unless the direction of the two road pieces are 100% the same, there will be gaps, which is what you see both with your original example with the effects, and the later one in the last post.

As for symbols, you cannot really attach these to each other. A symbol only have one node, the symbol origin (or placement point). You can attach them to a line or snap them to a grid, but using attach to make them line up won't work.

Normal print size for a battle map is 1" per square. A paper in A4 is 210x297 mm or 8-1/4 x 11-3/4 inches. That allow for 8 by 11 squares assuming the printer don't need huge margins, which gives a map size of 40x55 feet.

A3 is double A4, so 16 by 11 squares, A2 should be 16 by 23 and so on.

The important thing to remember about dealing with a path is that it is a primitive, it isn't a container for other entities like a sheet, symbol or multipoly is. As such, you cannot access the line segments in the path, because it doesn't contain any, it just contains nodes. So there isn't a way to get a reference to these before exploding. You can figure out what the lines will be by looking at the nodes in the path, but there aren't lines to get references to. (Also, changes in the drawing list can cause things to shift around in memory, so holding a pointer to an entity in the drawing list that was acquired prior to a modification may very well not be valid anymore.)

I haven't tried exploding from code myself, but I guess that would be the EExplode function. That function does have a parameter of type EXPPROC which looks like a callback function, maybe that could be of some use in determining the new lines, but I haven't really figured out how to use it properly.

If you make those palette swatches hotspots with appropriate macros, you can switch on a click without having to start the :CC2KEEP: command all the time. A bit more work to set up and change, but easier to use.