I have tried to update existing Coded Values in ArcCatalog > .gdb > Database Properties > Domains > Coded Values.
I am working on a land use map and solely need to add additional land use values (codes).
Once the changes are made, I open up ArcMap with a feature class from the .gdb I just updated. I do not see the new codes as options under Properties > Symbology nor when I edit the feature class attributes.
I saw a previous post for this topic for the online application, but I am working on ArcGIS Desktop 10.8.1
Please cross-check the following points.
1. After updating the attribute values cross-check with feature class attribute values in Arc Catalog whether it's linked or not.
2. If you linked the newly added coded values is linked with feature class than open arcmap and remove the feature class and add once again
3. Enable the editing model and open attribute table and check.
If problem still persists, please let me know.