What's the best choice to save loading date/time of an interface?

Hi everyone,

For audit purposes in a ticket management process, I need to track create/update/delete actions on a Ticket (record type) each time it has been opened the relative interface and track timing (basically: startEvent, endEvent).
I already track the interface initial loaded date/time in a local variable using now(), but how to pass it to a rule input (and therefore use it in the create/update process)? I think I have to use a!save in the primary button, but I am missing low-code details.

Do you have any suggestion?
Thank you so much,

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