A horizontal line of components on a message: up to 5 buttons, or one dropdown. You rarely need one: adding a button or a dropdown straight to a message builder puts it in a row for you. Build a row yourself to control exactly which buttons share a line.
The components inside a row, a container, a section, a modal or a message builder.
Add a component to it; the component is copied at that moment. Remove one by its unique id.
On a message builder, a bare button joins the last row of buttons when it has room, a bare dropdown gets a row of its own, and any container, section, text display, separator, media gallery or file display switches the message to components V2 (no content, no embed).
