I just looked it up on GitHub and it looks like you can override by pressing and holding the zap button.
https://github.com/vitorpamplona/amethyst/issues/235
According to #[5]
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Long press on the zap to setup custom amounts or double press on the zap to create a single custom zap with message.
Thanks!
Dumb question.... Where does the public message go when double tapped?
It goes into the zap message. Amethyst doesn't show that yet.
Got it! Thanks! It works now