Okay, so like, I'm aware the Character Viewer (⌘ + ⌃ + space) is displaying a system index of the full supported Unicode set of chars.
Z
**My question is**, is there a way I can take a glyph I've created in, say, photoshop or illustrator and either supplant/replace one of the system glyphs, or somehow bootstrap it into one of the Private Use Area (E000) blocks inside the unicode table? I totally understand this would be a *local only* modification and that nobody else would see it, as they would lack the custom glyph. That's fine. I'm even fine if the value of the glyph doesn't align with the visual output (so if I were to overwrite the letter "e" with billiard ball - this is a "'as a for instance," NOT my plan, lol - it would still sort between "d" and "f" still - this is not a requirement, just saying I wouldn't care).

This is for personal use on my own system.

Presuppose I have the relevant software to create and save the glyph in any format required, raster or vector, including the ability to make it into any flavor of font or graphic file. The objective here is to be able to add custom glyphs as labels to icons, or the system-ui for my own use. Nobody else who's not on my MBP need ever see it; I just wanna know if I can override or modify that table.

...I mean, it's gotta be stored SOMEWHERE on the drive, right?

Edit:
Okay, so, to further clarify: MacOS has a set of glyphs available to it by default, all built-in like, that it applies when rendering text. I favor using these when screen real estate is at a premium Example:
[![enter image description here](https://i.stack.imgur.com/Ph8Fn.png)](https://i.stack.imgur.com/Ph8Fn.png)

(above: Important, Work-Related, Shopping, Movies, Music). The full set of supported chars is viewable in the Character Viewer...  

[![Unicode](https://i.stack.imgur.com/PYvSe.png)](https://i.stack.imgur.com/PYvSe.png)

But there are still hundreds of open "slots" that have either never been filled, or are foreign language characters Apple didn't see fit to bother with.. When you see a blank white rectangle ('▯') this is an unsupported glyph\*.

So what I'm HOPING is someone knows how to actually not only make use of some of the open regions therein, but that also might know how to make the OS acknowledge their addition.

[![Private Use](https://i.stack.imgur.com/st8fb.png)](https://i.stack.imgur.com/st8fb.png)

\*Apple calls them "tofu" and has gone pretty far outta the way to preclude their ever showing on screen. Fun fact: the OS-Shipped Noto Sans ("Noto" == "NoTo" == "No Tofu") font contains the MAJORITY of available glyphs