Loom is keyboard-first. Every shortcut below is wired in Loom/App/LoomApp.swift via the standard macOS Commands API, so they show up in the menu bar too.
The number maps to the panel order for the current workspace kind. In a Prompt workspace the order is Terminal, Editor, Tasks, Agent — so ⌘⇧1 adds a terminal, ⌘⇧4 adds an agent. In an Ideas workspace ⌘⇧1 adds Notes, ⌘⇧2 adds Agent.