@Kuvick123 or @urban.tamas - If you run a long running query in the Editor using F9 and cancel it, does it cancel or does Toad hang or does it cancel in a timely manner? Using F9 is key here so if you normally run queries using Execute as Script (F5) then please try using F9 and cancelling. If you have the "Execute queries in threads" option checked (Oracle | Transactions page in Options) you can just hit ESC immediately to cancel. Toad will be responsive to mouse/keyboard clicks, but the Cancel button remains enabled and the green throbber at the right of Toad's status bar remains active. If the "Execute queries in threads" option is unchecked you can click Cancel on the progress dialog that shows and if Toad hangs the dialog never goes away and the timer continuously increments.
I spent some time last week and today trying to get to the bottom of this hang and what I'm seeing is that it's very specific to one of my databases using only a 19c or newer client. Coincidentally I cannot cancel a running query on this database using the same client combination. When Code Insight hangs for me it's after it has been cancelled once. This doesn't mean I have to explicitly cancel it, but just in writing the query it may run/cancel on its own. I can force the issue by using CTRL+T, clicking the cancel button, and then CTRL+T again.