Optional. The tab's cap and icon colour; defaults to the toolbar's ink. Push buttons take no ink.
kind
'tab' | 'button' | 'default'
Optional. <Toolbar.Button> only: 'tab' (the default) stands on the shelf; 'button' is a Standard push button
and 'default' the Default push button, centred in the bar, with a navy icon.
subtitle
string
Optional. In a menu: secondary text after the title, such as 'after Kenny G'.
badge
Badge
Optional. In a menu: a badge at the end of the row, such as 'AD'. Gold unless it names an ink.
onAction
() => void | Promise<void>
Optional. Throwing or rejecting shows the message beside the command; it stays busy while a promise runs.
action
VNode
Optional. <Action.OpenInBrowser>, <Action.OpenWindow> or <Action.ShowPopup>.
