Cannot use restrain option or opt/command/shift to make duplicates?

For others reading the solution nucomike round from Adobe Support. There are other third-party products (some of them browser extensions) which have a similar effect of diabling modifier keys in InDesign. You need to reboot your computer and run InDesign before any other application. Then gradually add other applications until you find the culprit!

These problems have not been an issue for most users of CC 2019 InDesign. Try trashing your preferences and see if resetting the program to its defaults clears up these issues.

To do so on a Mac:

The User Library folder in which InDesign’s preferences are stored is hidden by default on most Macintoshes. To access it make sure that InDesign is closed and click on the desktop to launch a Finder Window (Command-N). With this window in column view follow the path User>Home folder (it’s the folder with an icon that looks like a house—it may have the user’s name rather than “Home”) and click on the Home folder. With the Option Key pressed choose Library from the Finder Go Menu. “Library” will now appear within the Home folder. Within the Library folder find the folder called Preferences and within it find the folder called “Adobe InDesign” and the file called “com.adobe.InDesign.plist” and delete both that folder and that file. When InDesign is next launched it will create new preference files and the program will be restored to its defaults.

The advantage of manually deleting preference files in this manner is that after you’ve reset up the program (make sure that no document window is open) to your liking, you can create copies of your personalized “mint” preference files (make sure that you quit the program before copying them—that finalizes your customization) and use them in the future to replace any corrupt versions you may need to delete.