Sure, I will put forward your suggestion for an option in the Preferences - can you say what sites you are needing this for?
In the meantime, unfortunately it's messy to do it. You need to find this file:
(your home area)/Library/Preferences/com.shedworx.Jaksta.plist
The user Library folder will be hidden by default. To show the contents of it, click on the Go menu at the top of the screen and hold down the Alt key. Then select the Library item that appears. You should see a Finder window display the contents of the user Library folder.
If you can send us that file, I can modify it to enable that flag.