Click F12 or Ctrl + Shift + I to open the DevTools
Navigate to the Network tab
Enter interactions in Filter and select Fetch/XHR
Go back to Discord and click on the Button you want
Now you should see a new row show up in Network tab with name interactions, click on it.
Navigate to the Payload tab
Click on view source that next to the Request Payload
Select all the text in the payload and copy it
Done. that's it!
DevTools will only start recording network requests once it is open, so you must open DevTools first before clicking the button; otherwise, the request won't show up.