I have an external keyboard with a touchpad, like this. The touchpad had no physical buttons but it only emulates left click with a one finger tap and right click with a three finger tap.
With this setting it's not possible to drag and drop files or to make mouse gestures and so on, but if I could emulate somehow holding down the left mouse button using some key(s) on the keyboard, I'd solve the problem.
I already tried the universal access utility that lets you use the numeric keypad to emulate the mouse (it's an older model in which the touchpad can be converted to a numeric keypad with a swipe on the bottom, wtf :) ), but I did not manage to click and move at the same time, can you?
I also tried keynav, but did not like it much and couldn't do anything with it.
Hopefully it's a solvable problem!