Hi partner,
SLA condition does not support customization.
You could use Power Automate(FLOW) to do this.
For example you want to save the date and time when record fulfill the view criteria, you could create a scheduled flow and let it run per minute or even per second.

And then we create a "List records" action which will show all records which fulfill your custom condition.
So you could copy the view criteria to the filter line with condition statements.
like appointment is yesterday, we could use "UTCnow()" to get current date and time, use "AddDays(UTCnow(),-1)" to mean yesterday.

And when we find out these records, we should store the date and time to a field, so we create a update action, select the entity and instance, and then set the current date time "UTCnow()" to the field to record the time.

In this way, this flow will run per minute or second and if it find any record which fulfill the condition, it will store the date and time to a special datetime field on your form you've created before.
Best Regards,
Leo