You could use stats and group by _time and user :
index="_audit" action=edit_user NOT search | stats values(object) as object,values(operation) as operation by user,_time
If you have events that happen at roughly the same time but not the exact same time, and you want to group them together anyway, you could use bucket to do that. For instance to group together events that happened within the same second:
index="_audit" action=edit_user NOT search | bucket _time span=1s | stats values(object) as object,values(operation) as operation by user,_time
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