Corners is a Confusing Effect (naming, searching, and values)
This is a 2 part issue. I think the Corners effect is rather confusing both in what it does and once you figure out what it does the values structure is also confusing.
The Corners effect seems to act like a Skew & Perspective effect but if you search for either of those you won't find this effect. (I don't know how you can fix this but you don't need to rename it if you make it possible to search for either of those terms to find the Corners effect . . . maybe put those terms in parenthesis)
Once I figured out what Corners effect does, I was able to use it to make a cool 3D space grow and skew animation with keyframes so that is awesome BUT I had to trial and error how much for each corner because there was seemingly no consistency in how each corner was setup. Also when I wanted to go back to default of no skew I had to take a screenshot of a reset of the effect in order to put the values back since they are confusing in how they are set.
some of the corners are default at 1999 and others at 4000 but they don't seem to have any particular reason for that. I thought maybe it depends on which corner being farther from the top left or something but then Corner 2 and Corner 4 both have one of each value and they arent even consistent which axis is which value. I have no idea why it is setup this way and it makes working with this effect just very confusing.
Please, adjust the value system to have a default of 0 implying no change has been made and have that value set in the middle then we can add positive values or negative values to control the effect based on the direction on the axis we are adjusting. This is what I think would be ideal but something else would be fine too as long as it was consistent.