The Gradient Editor
The Gradient Editor is where all the main settings of the Gradient node are available.
Open the Gradient Editor
There are 2 ways to open the Gradient Editor:
- Click on the Gradient Editor button.
- Double click on one gradient pin.
Interface
The interface can be divided in 3 sections:

1: The Gradient view

The Gradient view lets you add, move and delete pins, and offers some options to modify your whole gradient in one click.
-Add a pin:
To add a pin, just double click on the gradient, or just below: the pin will appear below the gradient at the position you clicked.
The newly added pin value will correspond the already existing one in the gradient:

-Move a pin:
To move a pin, jusy click, hold and move left/right your mouse:

-Delete a pin:
To delete a pin, you can click&drag the pin to the top direction:

-Desaturate
As you would expect, this button will desaturate your graph:

-Invert Positions
Will reverse your gradient:

-Inverse Colors
Will modify each pin value by its opposite color:

-Interpolate
Switches the gradient computation mode from linear to interpolate
Linear mode
The linear mode is handling the transition between 2 pins, in a linear way:

Interpolate mode
The interpolate is handling the transition between 2 pins py interpolating the value of each one.
As a result, each pin is "keeping" its color a bit longer, and the transition between 2 colors is made in a shorter space compared to linear:

-Clear All
Removes all the pins of your gradient:

2: The RGBA Gradient key

The RGBA Gradient key lets you set the exact color and position of the pin you have selected in the gradient.
The Position spinner allows you to manually enter a value for the selected pin position:

The color palette can be used to visually select the color you want.
Select the hue with the vertical slider, then choose the position in the palette that represents the saturation and value of your choice

If for some reason you want to go back to your original color, just double-click on the bottom part of the color viewer:

The Pick button allows you to choose a color wherever on your screen:

The Invert button will simply invert your actual color and the To Gray button will desaturate your color:

The Copy and Paste buttons allow you to copy the actual color or to paste a previously copied color.
The sliders on the right give you the choice to work in RGB or HSV mode:

Since Substance Designer 6, you can now select and change the value of multiple pins at the same time.
3: The Gradient Eyedropper
The Gradient Eyedropper is one of the most useful features this node offers, as you can create complex gradients just by drawing a line on a reference picture.

The Precision spinner will help you adjust your newly created gradient by increasing or decreasing the number of keys: the lower their values, the more precise your gradient will match your picked values.