How to simluate mouse click + drag?

I know this isnt a direct answer to your question, but its a good work around.
Quite honestly, the desktop doesnt work well via touch screen, I would stop trying and use a mouse or a 3rd party program.

I use a program called TouchMousePointer by lovesummertrue: http://www.lovesummertrue.com/touchmousepointer/en-us/

It has been a life saver on the R7. I usually use an external mouse, but when I dont feel like messing with the mouse I just use this program.

So basically, you get a little mouse icon in the task bar next to the keyboard icon. Tapping this icon turns the entire touch screen into a track pad.

The best settings, in my opinion, would be to set it to full screen mode, single tap=click, and visualize pointer/track line=at working. I like to enable track line because it seems easy to loose track of the pointer with your finger on the screen.  It annoys me when using a mouse, but I always touch the icon to disable the program when using my wireless mouse.
There are other modes and settings you can tweak, but this is the way I like to use it. Using these settings, if you want to drag something you double tap and hold, then drag. That has also worked on just about every track pad I have ever used, so it's pretty much second nature to me.

The desktop screen just isnt designed to use a true touch interface, but this makes it workable without having to use the trackpad on the R7.

If you ask me, the R7 should come standard with some sort of program like this for use on the desktop.