How can I change the "frequently used" emojis in Discord?

Discord is chrome-powered. Hit control/cmd + shift + i to open up the chrome debugger tools. Hit Application tab. At the side, find the Storage column, open up Local Storage, and click on the discord url. These are all the stuff that Discord saves (including your password token - do not share pls thx). There is a key named EmojiStore if you clear the stuff to the right and reload discord with ctrl/cmd+r, it will be cleared. Otherwise, if you know how to manipulate JSON data types, you can litterally remove :frogface: from the history.

Source: https://www.reddit.com/r/discordapp/comments/79icxx/location_of_file_for_frequently_used_emojis_please/dp33x49/

For the JSON, it'll look something like this:

{"100":{"totalUses":1,"recentUses":[1514823987052],"frecency":50,"score":50},"eggplant":{"totalUses":1,"recentUses":[1514823987052],"frecency":50,"score":50},"fork_and_knife":{"totalUses":1,"recentUses":[1514823987052],"frecency":50,"score":50},"yum":{"totalUses":1,"recentUses":[1514823987052],"frecency":50,"score":50},}

So to remove "eggplant", for example, you'll want to delete the text starting from "eggplant" to the curly brace and comma that comes after "score".

{"100":{"totalUses":1,"recentUses":[1514823987052],"frecency":50,"score":50},"eggplant":{"totalUses":1,"recentUses":[1514823987052],"frecency":50,"score":50},"fork_and_knife":{"totalUses":1,"recentUses":[1514823987052],"frecency":50,"score":50},"yum":{"totalUses":1,"recentUses":[1514823987052],"frecency":50,"score":50}}

If you don't want to mess around in Local storage, there is a simpler trick to manipulate your Frequently used emojis list, as suggested by Kate Gregory in comments.

The first thing to understand is that this is a Frequently used emojis in messages list, not a Frequently used emojis in messages and reactions list, so using emojis to react to a message doesn't alter the emoji use count at all!

Knowing this, it becomes clear that to promote your preferred emojis into the list, just post a message with lots of copies of your preferred emoji, then delete your message. Keep repeating this until your preferred emojis are at the top of the "Frequently used" list.

If you want to remove emojis off the list entirely, then you will want to pick and promote any emojis below them in the list, and then add enough other emojis that the ones you don't want are pushed off the end of the list.