List of users who have opened the same record for either viewing or editing

Hi 

Please have a look to documentation https://docs.appian.com/suite/help/22.4/Logging.html#records-usage

This will provide you the user uuid list accessing the record. WIth the help of user function you can get the user name . for that 

add all users in a loop and check whose uuid is matching

"user who's currently viewing the record at the same time" is essentially impossible because there is no way to know (beyond super-vague guessing) when a user has stopped viewing that record.

What would your users do with the information that another user is concurrently viewing the same record? (I'm curious as to the business requirement here, not the "how do we do this?" detail)

Hi. 

This sounds achievable but with a catch. The easiest part of it is to store the username when someone opens a record. The hardest part it to clear the user context when they exit because user take no such action to exit which can be captured by Appian like clicking on a button or a link. 
So for that part, you have to assume a time (like 10 mins) or similar for which you think you user will keep the interface open. 

When you are good with the above part, you can simply use the text cache plugin and append the userContext to a cache (keep the ID of the record as the key) in the first local variable. 

And in the code, you can use that variable to show the list of users who are accessing it. Now just set the timeout of that cache to the limit you might have decided and that should do most of the work.