A simple way to customize characters is by using the variant glyph for each specific character.
For example, if you don't specify a variant, the black right pointing triangle will be displayed as an emoji like this:
▶
However, if you include the correct variant glyph, it will show up as text instead:
▶︎
Typically, using ︎
produces the text version, while ️
or no specification results in the emoji version.
Take a look at for a demonstration with examples like the left arrow and black heavy heart. Much of my knowledge on this topic came from