A field with a coded value domain displays a text cursor instead of a domain drop-down in the Attribute window when a subtype is applied to a feature class containing features.
This issue is not reproducible in the latest version of ArcGIS Pro.
解决办法
ArcMap: Alter the domain-coded values in the Attribute table, in which the drop-down appears. If a subtype option is assigned to the subtype field so that it is not 'Null' causes the domain drop-down on the domain field to appear in the Attribute window, export the feature class using the Feature Class To Feature Class geoprocessing tool to a new file geodatabase.
ArcGIS Pro: Alter the coded values in the Attribute window, in which the drop-down appears.