Ideally this question should go on isboxer.com forums in the Pro section, but that's okay.

The key here is actually in the first minute or two of the video.
https://youtu.be/Mizu6e6BEno?t=1m23s

The Sync Cursor Action occurs when you first click on the button, instantly followed by a click being sent to the healer window. The problem is that the game may not register the cursor movement before the click, despite happening first. You can work around this by splitting the "Left Click" mapped key (and the others here) into 2 Steps, with the first Step having only the Sync Cursor Action, and the second Step having the "Do Left Click in Virtual Healing". This way, the cursor moves when you press the button, and the actual click to heal comes when you let go of the button.