So, there’s two potential problems. Jordan identified one - the minimum screen size for the entire project.
Here’s the really bad news - if you open one of the particular windows in the designer, it’s probably going to be specifically set to exactly 1920x1080. This is a really common mistake people make when designing windows - targeting an exact resolution so that they can lay components out “pixel perfect”. Unfortunately, as Jordan points out, a 1920x1080 resolution doesn’t actually mean you have 1920x1080 usable pixels all the time, unless you run every client fullscreen all the time.
If what I suspect is the case is true (that the window itself was designed at exactly 1920x1080), there’s no “good” fix. You can try simply selecting every component in the designer, then shrinking them down by, say, 10%, then resizing the window dimensions themselves accordingly. Unfortunately, this will not work properly if anything is in ‘anchored’ layout mode. Outside of that, there’s no real fix, besides manually rearranging the components to fit a smaller size.