The compositor has zoom capability. The pull-down menu on the bottom of the compositor window has a number of zoom options. When set to Auto the video is zoomed to match the compositor window size as closely as possible. When the video is zoomed bigger than the window size, you can use scrollbars to scan around or if the zoom icon is enabled, the middle mouse button can be used to zoom in or out the video.
The zoom toggle also causes the Compositor window to enter zoom mode. In zoom mode, clicking in the video output zooms in while a Ctrl-click in the video output zooms out. If you have a wheel mouse, rotating the wheel zooms in or out too. Zooming in or out with the zoom tool does not change the rendered output. It is merely for scrutinizing video or fitting it in the desktop. Playing video on the compositor when zoomed to any size other that 100%, the original size, requires CINELERRA-GG to do extra processing steps. This could affect performance on slower systems
The CINELERRA-GG Community, 2021