Contract Manager

If you use «Contract Manager» with operating system macOS Sierra 10.12.x, you have the possibility to open document windows as a TAB, rather than as a stand-alone window.

Example:

Main window of «Contract Manager»

Main window of «Contract Manager» with additional categories window as a TAB.

If you open the the address book window, you can't drag a contact into the "Contractor" field in the main window, because it is not visible at the moment. To work around this problem, you can turn this window back to a normal window. Just drag the "TAB window" out of the application (see video).

In macOS Sierra, you can specify whether to open new document windows as a tab in System Preferences. To do this, select Menu => Preferences => Dock.