Custom styles are the answer. Just define a named character style "Awesome", or perhaps "Emoji" in case you change fonts with the right font in the right size[^1] in your reference-doc, and then in your markdown source:
[👍]{custom-style=Emoji}
[^1]: This is assuming that your "word processor" can handle color fonts. If not Symbola is a good b/w alternative.
If you do this a lot a Lua filter can save you some typing:
``````lua
function Span (span)
if span.classes:includes"emoji" then
span.attributes['custom-style'] = "Emoji"
return span
end
-- else
return nil
end
``````
Now you can just type `[👍]{.emoji}` and run pandoc with this filter.
It works the same with divs and character styles.