Unable to find the button to show the SQL Statement during Data Compare in Toad. The icon is located in the upper right corner of the comparison to show the SQL statement on each tab of the process, Source tab, Target tab and Differences tab.
In 13.1 the option to show SQL statement is no longer available, however it can be enabled manually, see more details in the workaround

WORKAROUND
After saving the change and start Toad for Oracle again, it should look like this:
