The following bookmarket shows a popup with the name of the participants separated by newlines.
javascript:-function(maxStrLength = 2000) { try { function findParticipants(current, depth = 0) { if (depth > 7) return; if (typeof current !== "object" || current === null || current === window) return; const descriptors = Object.getOwnPropertyDescriptors(current); for (const prop in descriptors) { if (prop.startsWith('["spaces/')) return Object.values(current); const item = findParticipants(descriptors[prop].value, depth + 1); if (item !== undefined) return item; } } const rootState = Object.entries(window).find(x => x[0].startsWith("closure_lm_"))[1], participants = findParticipants(rootState), names = []; function findName(obj) { for (const prop in obj) { const value = obj[prop]; if (typeof value === "object" && value !== null && typeof value[1] === "string") return value[1]; } } for (let i = 0; i < participants.length; i++) { const name = findName(participants[i]); if (names.indexOf(name) === -1) names.