In the table, the changed event seems to work and, it is possible to acquire information about the modified row.
You may check the sample code from the page below.
Acquire the changed field and row object within the table:
It seems to be not working because the value is not being output by the following process that appointed the field directly.
→ There is no information about 'qty' after 'record.'
Please check if the event occurs by changing value within the table to refer to, like one below.
Hopefully, this solves the issue.