[Brian_K_White]

No not symbol modifier. Compose.

To get a particular glyph, or control code, you have to compose it out of multiple keypresses.

Some common examples happen to be modified versions of whatever glyph happens to be on a key, but that is just a subset, arranged that way for human sanity, humans would hate it if you had to press shift+g to get A, and really only in the latin languages whose writing even works that way. The glyphs could actually be anything, and outside of the latin languages they are. The poop emoji is not a modified form of any number or letter.

And it's not even just glyphs but any byte or byte sequence you want to produce. A single 0x01 byte is not a glyph, nor a modified form of any glyph, but you can still type it, and it's composed of the CTRL key and the A key.