DisableMonitor is described as 'Adds the missing feature to disable a monitor on your Mac!
Easily disable, enable or change the resolution of a monitor!'. There are four alternatives to DisableMonitor for Mac and Windows. The best alternative is Dual Monitor Tools, which is both free and Open Source. Other great apps like DisableMonitor are Ultramon (Paid), SwitchResX (Paid) and EasyRes (Free).
- UltraMon is a utility for multi-monitor systems, designed to increase productivity and unlock the full potential of multiple monitors. View 15 alternatives to Ultramon
The program seems no longer updated. Last version, 3.4.1, released in October 2018, can be still downloaded from the official website