Found mention of it in the 10.2.300 feature release document:
Epicor Web Configurator
You can mark configurators as Epicor Web Configurator (EWC) and deploy them to Epicor Web.
When you enter a configurator record and set it to EWC, all Client processing is moved to the web and the
existing Server side logic remains in the Epicor ERP application. For example, if you launch the EWC configurator
from within a sales order, you open an iFrame and hand off control to the EWC team. The EWC team will deal
with any Client side events and make the appropriate calls to the server for Keep When rules, part swaps, and
Server side User Defined (UD)/Lookup Methods. When all is complete, they will call into the Configuration Runtime
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10.2.300 Feature Highlights 10.2.300 Feature Highlights
service method to save the configuration. The EWC configurators have the ability to apply CSS so your configurators
include a more modern look.
Setting configurators to EWC enables you to use the TypeScript open source programming language that supports
the Kinetic technology used by EWC configurators. You enter TypeScript expressions in the Code Editor as well
Configurator User Defined Methods Maintenance that includes the TypeScript sheet. Use the sheet to create
an expression for a desired user defined method.
In this release, Epicor Web Configurator will support a limited set of UI features. More UI features will be made
available in subsequent releases.
Note You can also enter TypeScript expressions for Dynamic Lists (Configurator Designer).
Note To use Epicor Web configurators you must install the Epicor Configurator 10.2.300 license.
Menu Path: Sales Management > Configurator Management > General Operations > Configurator User Defined
Method Maintenance