Swimlanes.io is a free webapp for making sequence diagrams. You simply edit the text on the left and the diagram is updated in real time. You can download your sequence diagrams as images or distribute with a link.
Title: Reminders App User -> WhatsApp: Create Reminder to XYZ at <REMINDER TIME> WhatsApp -> App: Create Reminder (webhook) App -> Temporal Cluster: Start Reminder Workflow Workflow Worker -> Temporal Cluster: Start Workflow Execution note Temporal Cluster, Activity Worker: *wait for <REMINDER TIME>* Activity Worker -> Temporal Cluster: Get Reminder Task Activity Worker -> WhatsApp: Send Reminder message WhatsApp -> User: Remember to XYZ