Thanks a lot! I have got better. Now another problem. Button Alt + Crop doesn't work even after the function Reset Transform.You add 2 sources, one is your webcam which you place to the left, the other is a window capture of the app with your text you place to the right of the OBS preview. To cut unwanted margins or bring the webcam to a vertical rectangular shape, explore the crop function: press and hold the ALT key, then drag the source handles in the preview to crop.
Aim precisely at small red square elements of the bounding box of the source in the Preview window of OBS (the source should be selected first, by clicking on its name in the Sources list; also, if whole Preview window is locked - you'll must unlock it by using right-click menu option named Lock Preview).Button Alt + Crop doesn't work...