The selection toolbar shows up when you highlight a portion of your script. It allows you to access a variety of editing tools and other features quickly:

• Ask Underlord — start a conversation with Underlord, Descript's AI co-editor.
• Change layout — opens the layout picker. If a layout is selected, applies the layout to the selection and creates a new scene
• Add layer — Add new layers right in the Script Editor—like imported files, stock media, text, captions, shapes, or recordings.
• Add scene — Opens the layout picker so you can quickly apply a layout to a scene.
• Correct — This will allow you to correct the text of your script without affecting the audio.
• Regenerate — Make a correction or smooth out an edit with Regenerate. 
• Edit your script — choose to ignore your selection, delete it, replace with a gap clip, or just  correct the transcript without editing the underlying script audio or video..
• Make your text selection bold or italic.
• Highlight — Highlight sections in your script in different colors. You can then use Copy highlights to aggregate your highlighted sections in a new composition.
• Duplicate to... — Quickly copy selections to a new or other compositions in your project.
• Add comments — Communicate and collaborate with your teammates by leaving comments and reminders in your script.
• Ellipsis — Display the right-click menu for your selection.