I have currently not updated to V10, but this is an example how it works in V8x and V9x.
Update rule
If Booking WAS CHANGED Then CREATE SystemLog WITH
SystemLog.ChangesMade=GET_CHANGES(Booking)
Form of SystemLog
Displays the value of <<SystemLog.ChangesMade>>
Open the form and it renders a table of all the modified attributes like this:
Modified instance 13960161 of Booking
| Attribute | Old value | New value |
| JobInfo | Not booked | Booked |
| ContactPerson | Alice | Bob |
Unchanged attributes will not be rendered.