Xcode11 Editors (via "Add Editor to Right") are disabled

Assistant Editor

Assistant is now under the editor option menu (left itme).

Also you can use control+option+command+return shortcut

Add Editor

The other one that is disabled is Add Editor on Right. Some times its getting disabled because there is not enough space to show another editor. You can change the position of it to below by holding option and click. This will convert it to Add Editor Below

Unfocus the Editor

Turned out to be that Editor was in focused mode. As soon as an editor is in focused mode, Xcode hides the other editors and disables "adding editors to right" option on the menu and right bar.

Use the following key combination to toggle the focus-unfocus the editor.

Control + Shift + Command + Enter

Or use the