Notices
Notices are a Discord-specific term for a banner-like element that appears at the top of the screen. In Discord this is most often used to either give persistent information or passively wait for user interaction.

Showing Notices
This function has the same signature as showToast with the except that content can also be an HTMLElement. This allows it to be a bit more customizable. However, most of the functionality you would need is included already.
BdApi.UI.showNotice("This is just a basic informational notice!");Result

They can do more than just show information though, you can also add multiple buttons for the user to interact with.
BdApi.UI.showNotice(
"This is just a basic informational notice!",
{
type: "error",
buttons: [
{
label: "Click Me!",
onClick: () => console.log("Clicked Me")
},
{
label: "No Me!",
onClick: () => console.log("Wrong One!")
}
]
}
);Result

Notice how this time we used type: "error" and it became red. This has the same type and styling options as showToast.
Each of the buttons here act completely independently which allows for powerful combinations. Additionally, you can have the notice close after a set time using timeout. This is a number of milliseconds after which to close the notice. If set to 0 (the default), it won't close until closed by the user or the caller.
showNotice returns a function which allows the original caller to close the notice either earlier than the timeout or without user interaction. The onClick of the button is provided with this same function as the only argument.