Are you referring to an admin covering for you or you’re helping a user prepare for being out (ie reassigning tasks due during that time to someone else, sharing templates, etc.)?
If the former, of course instance documentation is key. What worked well for me when I left a position and a new admin was taking over was I created a WF project called ‘WF Instance Documentation’ and used that to put info in task details, upload relevant docs, etc. I organized it by having parent tasks for topics like reporting, integrations, request queues, etc. were all parent tasks. Under them were tasks for specifics with info in task details. So under the integrations section, had a task for each integration we used with any info the admin should know (contacts, ‘user profiles’ set up for the integration if relevant, etc).
Let me know if this makes sense! Really wanted a way to have documentation live IN WF and not in disparate places. Practicing what we WF admins preach 😃