I’m not going to e-mail @drdrang, but instead post my suggestion to this post on his website here.
I’m using Fluor to manage the working of the function keys.
In the words of the developer:
Fluor is a tool that allows you to automatically change the behavior of the keyboard’s fn keys depending on the active application. It’s that simple.
As it seems to be a lesser-known utility, i think it’s worth a post on MPU.
I’m not very familiar with Karabiner, but I think Fluor serves a different purpose. It’s ‘just’ meant to automatically change how your function keys work. Based on the active application.
I don’t use KE because I couldn’t get it to do what I wanted, however a quick look at the documentation doesn’t seem to say anything about being able to operate on a per-app basis.
Interesting little app 
Maybe it’s a stupid question, but does it works the same on Touch Bar Macs?
It appears that Fluor switches between special behavior and standard function key behavior based on the current app. While I can see that being very useful for some, it isn’t for me. I want F5 to work as a Show Desktop toggle no matter what app is active.