The mouse is often not the best way to make selections or do operations in UF.  For many functions, the arrow keypads are more sensitive or faster and are manually easier than the mouse.  Here's how to activate the arrow keypad:

1.  Select a function from a drop down box or move a slider with your mouse
2.  Continue by holding the shift key and pressing either the left or right arrows.

Confused?  Try these examples:

Drop Down Boxes

1.  Make a two layer fractal (anything will do)
2.  Select the "layers" tab in the properties toolbox and activate (highlight) the top layer
3.  Select any new merge mode using the mouse
4.  Hold down the shift key and the hit the right arrow key....  hit it again.

You will see the merge modes changing.  You can quickly step through all the merge modes in this way then go back using the left arrow key.  This is much faster than using the mouse to select the next merge mode and is very helpful in exploring your image.

Sliders

1.  Using the same fractal, activate the gradient editor
2.  In the editor, move the large slider just a little to either the right or left
3.  Hold down the shift key and then press the right arrow continually.

You will see the gradient for that layer only cycle slowly.  If you press the arrows quickly, you can make very fine movements to the slider.

This methodology works with nearly everything in UF and is a great time and frustration saver.