I think we might have a Scripted Function somewhere that does that. I will check with the devs when they're back on Tuesday.

I have a script that does pretty much what you want, but I've never posted it because it isn't very reliable. Sometimes certain windows ignore the command to make them transparent, which looks pretty jarring. But with that being said, here's how to get the script into DisplayFusion:

• Download the file named "Make Other Windows 75% Transparent.txt" attached to this post
• Open the DisplayFusion Settings window and go to the "Functions" tab
• Select Scipted Function->Add Scripted Function
• Paste the contents of the file you downloaded in the first step into the window that pops up
• Optionally review the code and give it a key combination
• Click OK, then OK again to save and apply your changes

The script would probably make the most sense with a "Window Focused" Trigger. Here's how to set that up:

• In the DisplayFusion Settings window, open the Triggers tab and press the "Add" button
• In the "Event" dropdown, select "Window Focused"
• Enable the "Process Filename" checkbox, close the window that pops up, and type *.* in the textbox
• In the Actions list, click "Add"->"Run Function", and select the script you added in the above steps
• Click OK, then OK again to save and apply your changes

I've included another script, called "Make Every Window Opaque" that will reverse the effects of the Trigger in case things go awry.

Now, with all of that out of the way, I would like to suggest an alternative to your transparency feature. It's called "Monitor Fading", and you can enable it by going to the "Monitor Fading" tab on the Settings window, and setting up a HotKey that will enable and disable it at will. The "Fade Everything Except Current Window" mode should work the best for you.

Thanks!