I used it several times for the generation of subsets over many images. You can find it under
Add > Raster > Geometric > Subset
It is important that you are clear about the difference between pixel coordinates and geographic coordinates.
Pixel coordinates are tricky in the batch mode because you likely have shifts between different images, especially when using data of different tracks. Geographic coordinates are good but as long as your data is unprojected (if you want to subset SLC products) the geolocation may also shift a little bit. So don’t choose a too narrow subset window.