It is not possible to preselect an option in a comboBoxField or checkBoxField when using some dialogs in the new framework.

I was able to make it work within the pages app, under a component dialog but it is not working for any action dialog that I have tested.

Steps to reproduce

1. Go to the Assets app and click on "Upload Zip archive". Note that there is no preselected item in the encoding field and that the contentstream label is missing.
   
2. Go to the Resources app /dam-app-jcr/dialogs/upload.yaml
3. Open the file, note that there is a defaultValue, let's also add the selected: true property and save:

   !inherit:ui-framework-jcr:import
   form:
     properties:
       encoding:
         $type: comboBoxField
         defaultValue: UTF-8
         datasource:
           $type: optionListDatasource
           options:
             UTF-8:
               value: UTF-8
               selected: true
             CP437:
               value: CP437
   
   actions:
     commit:
       class: info.magnolia.dam.app.action.UploadAssetsActionDefinition
       availability:
         root: true
   

1. Go back to the assets app and see that there is still no preselected item.

I tested it both with comboBox field and CheckBoxField and neither is working

(It is possible to change the contentstream label in /ui-framework-jcr/dialogs/import.yaml but this should be added for all customers)

Changing directly the dialog definitions in /ui-framework-jcr/dialogs/ does not make the preselect work either.

Expected results
If we add a defaultValue or selected: true, that value should be initially selected in the dialog
 
Actual results
There is no preselected value