I don't think I've ever used the Query Builder button. Usually to create a Recordset I just go to the Bindings panel, click the Plus icon and choose either Recordset (Query) or MySQLI Recordset (Query) (both work the same as long as the connection you choose is a MySQLi connection). Then in the Database items list I choose the table & column I need from the dropdowns and click the Select button, then repeat for each column you need to include. Then use the Where and Order By buttons in the same way. You can also add variables in the same window. If you need a more complex query such as joining tables, I usually find it easier to code this by hand by adding in the necessary joins after the recordset info has been added and then testing it in something like HeidiSQL.
You could also try clearing the Dreamweaver cache by deleting the cache file (on Windows located at C:\Users\[username]\AppData\Roaming\Adobe\Dreamweaver CC 2019\en_US\Configuration\WinFileCache-[randomString]. dat) - close Dreamweaver, delete file, restart Dreamweaver.
