Add a rectangle outside captured source

[Hetz BH]

Hi,

I used Camtasia before for capturing screen, and it has a nifty feature - which add some rectangle outside the captured area, so you can see on a single screen - what are you capturing. With OBS, I need to use 2 screen and see on the 2nd screen (where OBS is running) what am I capturing.

Is there a way to add a rectangle outside of the captured area?

Thanks