Solution
There is no product called "TestStand Custom Sequence Editor" available for download on ni.com. A custom sequence editor refers to a TestStand user interface that you develop using one of the supported programming languages—similar to how you create Operator Interfaces—but with added sequence editing capabilities.
You can create a custom sequence editor to suit your needs in a variety of programs and languages, such as LabVIEW, LabWindows™/CVI, C++, and C# using the TestStand Development System license.
You will need a TestStand Custom Sequence Editor license on every machine where you deploy a test system that includes your custom sequence editor. This license allows you to develop and edit test sequences and sequence files within the custom sequence editor.
For the TestStand Custom Sequence Editor license, please contact NI. You can activate the TestStand Custom Sequence Editor by adding the license file in NI License Manager.