Edit #1: Found it! It's PMAIL.INI. The entries are "Quick folder definition". Odd that my initial search for "Quick" did not find anything.
I was about to answer you when I realized you've found the answer yourself.

It's also worth mention that
Quick actions are Identity driven. Changes made in an Identity will affect only that Identity.
Edit #2: I can't find a way to remove a quick action from with Pegasus Mail (eg: set it back to "Undefined" ).
There is not a button or shortcut to do that, at least not documented. You can trick Pmail to disregard a previous (undesired) setting by indicating a false one in the destination field triggered by the
Select button. Let's say you have a quick action
"Move to Pmail folder" active that you want to disable. Change the action to
"Apply a set of filtering rules to the message" but DO NOT click the
Select button, then click
OK. As it won't make sense to Pmail it will be tagged "Undefined" and disabled.
Also, you can go to PMAIL.INI and change the line (no quotes):
"Quick folder definition = 10F8BFC5:7634:FOL07C8E, 0, 0"
to
"Quick folder definition = "
Another thing to mention is the Quick action order. Which line is triggered by Ctrl+1 or picked as Quick action #1 in the menu? Well, the first Quick folder definition line found in the PMAIL.INI section of the working Identity. So, if one have plans to make Quick actions "universal", everyone must have the same set of Quick folder definition lines, in every section of PMAIL.INI, and in every PMAIL.INI file. BTW, I did not test any of this thoroughly but it is what makes sense to me. I'm open to questioning.
Going a bit further there's a way to put Quick actions buttons in the Pmail toolbar. Below is a snippet of what I use here regularly, except by the #2:
0,10311,0,1836,"Open/Move to Spam/Junk folder (Ctrl+1)"
0,10312,0,1836,"Forward message to Admin (Ctrl+2)"
0,10313,0,1836,"Open/Move to Pegasus Mail Private folder (Ctrl+3)"
0,10314,0,1836,"Open/Move to NotSpam folder (Ctrl+4)"
0,10315,0,1836,"Open/Move to -Avisos folder (Ctrl+5)"
0,10316,0,1836,"Open/Move to Transit folder (Ctrl+6)"
So, as long as properly set, every user can have a button to forward Admin any message at once. And I can't resist to say what I've heard from the Pmail Community since day one: "There is nothing comparable to Pegasus Mail." Period.
Thank you, David! 
[quote="pid:57464, uid:28772"]Edit #1: Found it! It's PMAIL.INI. The entries are "Quick folder definition". Odd that my initial search for "Quick" did not find anything.[/quote]
I was about to answer you when I realized you've found the answer yourself. :) It's also worth mention that **Quick actions** are Identity driven. Changes made in an Identity will affect only that Identity.
[quote="pid:57464, uid:28772"]Edit #2: I can't find a way to remove a quick action from with Pegasus Mail (eg: set it back to "Undefined" ).[/quote]
There is not a button or shortcut to do that, at least not documented. You can trick Pmail to disregard a previous (undesired) setting by indicating a false one in the destination field triggered by the **Select** button. Let's say you have a quick action _"Move to Pmail folder"_ active that you want to disable. Change the action to _"Apply a set of filtering rules to the message"_ but DO NOT click the **Select** button, then click **OK**. As it won't make sense to Pmail it will be tagged "Undefined" and disabled.
Also, you can go to PMAIL.INI and change the line (no quotes):
````
"Quick folder definition = 10F8BFC5:7634:FOL07C8E, 0, 0"
to
"Quick folder definition = "
````
Another thing to mention is the **Quick action** order. Which line is triggered by **Ctrl+1** or picked as **Quick action #1** in the menu? Well, the first **Quick folder definition** line found in the PMAIL.INI section of the working Identity. So, if one have plans to make _Quick actions_ "universal", everyone must have the same set of **Quick folder definition** lines, in every section of PMAIL.INI, and in every PMAIL.INI file. BTW, I did not test any of this thoroughly but it is what makes sense to me. I'm open to questioning.
Going a bit further there's a way to put **Quick actions buttons** in the Pmail toolbar. Below is a snippet of what I use here regularly, except by the #2:
````
0,10311,0,1836,"Open/Move to Spam/Junk folder (Ctrl+1)"
0,10312,0,1836,"Forward message to Admin (Ctrl+2)"
0,10313,0,1836,"Open/Move to Pegasus Mail Private folder (Ctrl+3)"
0,10314,0,1836,"Open/Move to NotSpam folder (Ctrl+4)"
0,10315,0,1836,"Open/Move to -Avisos folder (Ctrl+5)"
0,10316,0,1836,"Open/Move to Transit folder (Ctrl+6)"
````
So, as long as properly set, every user can have a button to forward Admin any message at once. And I can't resist to say what I've heard from the Pmail Community since day one: _"There is nothing comparable to Pegasus Mail."_ Period.
Thank you, David! :)
-- Euler
Pegasus Mail 4.81.1154 Windows 7 Ultimate
IERenderer: 2.7.2.2 AttachMenu: 1.0.2.0
PMDebug: 2.5.8.37 BearHTML 4.9.9.6