This menu can be used to add or modify a straight accelleration projectile effect. These effects can be used to make projectiles speed up or slow down during its flight. This effect is useless as impact effect and only useful as in-flight effect. The menu should look like this:

There should be a 'Cancel' button and an 'Apply' or 'Create' button. Also, there should be edit fields for the minimum and maximum accelleration.