any upgrade or install is a single install not an upgrade. it installs in a new directory each time. no cleanup is done. Can the installer choose to clean up old versions or keep old version with a radio button. this will make the installer better and save time if someone has to do manual cleanup.
Many users prefer to have multiple versions of Toad installed side by side. To achieve this, the version number is part of the install folder path and settings path. When you install a new version, it should copy the settings from the prior version.
However, we do have a subscription version that upgrades the way you are asking - without version numbers in the install path or settings path. Product Support - Toad for Oracle Subscription
I'm not involved in licensing or sales at all, so I can't promise this, but maybe your license can be converted to the subscription model. You might want to talk to Quest Sales or Support to see if that's possible.