Should the directory list people or roles?
Roles first, with people attached. That way a departure changes one line instead of invalidating the file.
How big should it be?
Start with the seats that get asked about most — approvals, escalations, access requests, scheduling, invoices. Ten strong rows beat sixty vague ones.
Does this work across time zones?
Fill in covered hours and a backup for every seat. A global team needs to know who is on shift, not just who owns the work.
Is anything I type here saved?
No. It all runs in your browser and nothing is sent anywhere. Use the export button to keep a copy. Do not put personal employee data in it — internal role addresses are enough.