I don't think that is possible with just StrokeIt. You could set Right Mouse Button + Middle Button to do Control Click, though:
- Have the right mouse button as your standard gesture-triggering button in the preferences menu
- Make an action that gets triggered by MButton
- Add a command to it: Hotkey, control click; you do need the Emulate Mouse plugin for that, though. You can find the link to it somewhere on the forum; if you can't find it, I could put it up on the internet somewhere.
But it would be much easier to accomplish Middle Button triggers Control Click if you used a simple Autohotkey script:
#Ifwinactive, Total Commander ;limits the script to this program
Mbutton::^Lbutton ;the caret ^ means Control
#Ifwinactive
Download AHK, install it. Make a new text file and paste the above code into it. Rename the file to whatever.ahk, and double click it. Now your hotkey is active, unless I made some stupid mistake. I don't have TC installed at the moment, so it could be that you need a different identifier with Ifwinactive. What I just did here works only if "Total Commander" is actually in the title bar of the application. You can change that to a different phrase if you see that in TC's actual title bar. Good luck!