Text rules replace every match of their text. They run first.
Regex rules take a JavaScript pattern like /hello/gi. Without slashes, a pattern uses the g flag.
Any rule can have a condition, so it runs only when the message contains some other text.
Settings
There are no rules until you add one.
Test your rules shows the tester. Type into Example message and Result shows it after your rules run. Open by default.
Export & share copies both rule lists as JSON and opens the share sheet.
Import clipboard and Import pasted load a ruleset from the clipboard or the Paste JSON field.
Rule type switches between the Text and Regex lists. Text by default.
Add text rule and Add regex rule open the editor. Fill in Find text or Pattern, Replace with (\n for a new line, blank to remove), and the optional Only when the message contains.