There is certainly a simple way to hide any text on Discord. The fastest way is to type two vertical bars before and after your message. It looks like this: ||your secret text||. When you send it, the message appears as a black box. Others just click or tap the box to reveal what you wrote.
If you're using a computer, there's a shortcut. Highlight the text you want to hide before sending it. A little formatting menu will pop up, just click the eye icon. It adds the hidden formatting for you automatically!