I am going to give two ideas for how to improve keyframing, first one is probably the easier one to implement.
With the transform effect, directly above or below the x and y coordinates should be a thing which allows you to change the speed at which x and y coordinates are changed through the mouse wheel or arrow keys. The reason that this would be useful is because at the moment if you go off center in the image or a video too much, the x with the circle in it disappears, that means that you no longer will be able to move the video or the image with a simple hold of a right click, rather the next best option becomes scrolling through coordinates, but the speed of change is too slow at the moment and tinkering with them by changing the values directly is also time inefficient. Having the ability to easily speed up and slow down the speed of change would improve time efficiency and also accuracy.
Now this other suggestion I realize is probably asking a lot but I honestly think it would make the keyframing much better in terms of time efficiency. The suggestion is to create a transform-keyframing effect that is pretty much the exact way vegas pro does keyframing. The vegas pro keyframing at all times gives you a view of what is shown in the video while also giving you a view of what is not shown in the video, seeing what you don’t plan to show in the video is useful because it immediately allows you to know where to place the screen and how to do the keyframes. In more practical terms, imagine there is an image with numbers placed right at the left end of an image, then let’s say I want to avoid showing those numbers, say I want to do a slide keyframe effect from the right of the image to the left, with vegas pro I instantly know where the screen is relative to the image so I also instantly know where the last keyframed screen will be such that the numbers are not shown, I don’t need to move around a zoomed in image a bunch in order to know exactly where the last keyframed screen should be. There are other scenarios where the vegas pro style of keyframing makes more sense in terms of time efficiency. However, just in case there are scenarios where the current kdenlive style of keyframing makes more sense, for that reason that style should be kept as well in case vegas pro style of keyframing gets implemented.