Background
This is the umbrella ticket for all tasks related to adding a new feature to TemplateData itself, to the TemplateData editor, and then to the VisualEditor template dialog.
We are adding the ability for users to specify a list of suggested values to a parameter in TemplateData. These will then be displayed to users who add or edit the template in the VisualEditor in the form of a dropdown. They will then have the option to select one of the suggested values or type in a custom value. If a custom value is chosen, it will display a notice.
We implemented on the test instance prototype to very positive feedback in usability testing.
Related phabricator tickets
T53375: TemplateData: Add parameter type for selecting one of predefined values (like "<select>" or ENUM)
T52760: TemplateData: Support suggested values
Prototype implementation on test instance: T260157: VE Dialog on the Test Instance: Add ENUM parameter type to Template Data and add combobox to VE