Click OK to save that window to be recorded.In the Window dropdown, find your program window that you want to record and click it.Click on the scene name you just created in the same white box, then in the white box to the right labeled Sources, right-click and do Add -> Window Capture and enter any name you want to identify the window capture as.In the main screen of OBS, right-click on the white box in the bottom left labeled Scenes, click Add Scene, then enter any name you want to identify the scene as.Click OK to save and apply the settings you just changed.Set File Path to wherever you want the recording to be saved to.In OBS, go to Settings -> Settings then go to Broadcast Settings and set Mode to File Output Only.Open OBS and the Program you want to record.Here's a step-by-step on how to go about recording a specific window: (Note: it cannot record minimized windows, as minimized windows will stop rendering completely).

It's a Free and Open Source program that allows you to record both your screen and specific windows.

Screen record with obs