There are two options to change the table.
The first one is explained in article Swap tables easily.
The second instruction is listed below:
Go to your Table Management Panel and click on Reservations
Check the date and find the reservation you want to edit
Click on Edit
You will see the table that has been assigned to the guest.
For changing the table you need to click on that table and uncheck it and choose
the table you want to assign. Save the changes.
You can select more than one table based on the number of guests.