If my laptop is lost or stolen, can I log Spanbox out remotely?

Your sessions are stored locally, so first protect the laptop itself with a login password plus FileVault (Mac) or BitLocker (Windows), that's your main defense. To cut access remotely, use each app's own 'linked devices' or 'active sessions' setting (WhatsApp, Google, Slack, Discord all have one) and sign that device out, which kills its Spanbox session too. Since there's no Spanbox cloud account, the app-by-app remote sign-out is the lever.