Just a suggestion:

What we do for disabled controls, is have an option in the contextual menu when clicking right mouse button which says "Copy contents". We don't use the readonly attribute.

Hi Valdas, Set a custom theme for those objects that you want to appear different color than the rest of your app AND set the themes to disabled using "{“drawing”:false}" command.  Read the "Custom theme definition files for selected objects or controls" and "How to turn off UI Theme at runtime" sections of this tech article: https://community.appeon.com/index.php/articles-blogs/tutorials-articles/2-powerbuilder/301-applying-a-new-ui-theme-to-your-application-2

{
 "meta-info":
 {
  "version":"190"
 },
  "w_main.uo_1.cb_1":
 {
   ...
   // Copy the settings from the "commandbutton" node of
   //the "theme.json" file and then modify
 }
  "w_main$commandbutton":
 {
   ...
   //Copy the settings from the "commandbutton" node of
   //the "theme.json" file and then modify
 }
  "w_main":
 {
   ...
   //Copy the settings from the "window" node of
   //the "theme.json" file and then modify
 }
}

I think you have done what you asked for in order to make a disabled field selectable:
1.  Set taborder of the field > 0.
2.  Set Edit property DisplayOnly.

If you want a specified set of options for the user, use the RMBUTTONDOWN event to invoke options you can add to the popup DW menu.