There's a documented method for scrolling through the gradients in your gradient preset before selecting one for your image, which is to click on the gradient icon and use the < and > keys (add Shift to jump to the top or bottom of the list).
But what if one wants to first open the image and then quickly scroll thru the colored gradients in a preset to immediately see how the colors of the image are affected?
Here is the procedure:
--open the image
--click on New Adjustment Layer>Gradient Map
--change the blend mode to soft light
--double-click the gradient icon on Layer 1 to bring up the gradient map dialog
--clkck on the resulting icon Gradient Used for Grayscale Mapping
--in the resulting Presets dialog, click on the first colored gradient
--use the right-arrow key to scroll thru the remaining colored gradients in the preset
In this particular case I am using the custom gradient that I created and gave the title Warm Cool Image (the 7th from the left in the top row).