Any plans on bringing this back? It had functionality that I find impossible to replicate in BP.
I am currently for example trying to make footprints that the player leaves behind. Rendering the decals behind the players works well, and I even got them to automatically disappear after X seconds using the build in lifetime for decals, but I cannot find any way to make them fade out before disappearing.
Material instance time varying would be most helpful for cases like mine.
In the case of fading out a footprint you can do it much more efficiently than having the CPU updating an alpha value every frame. When you spawn the footprint, set a value on the material representing the time at which the footprint was spawned. In your material you can subtract that number from the current game time and multiply it by (1 / DesiredLifetime). That will boil down to a single instruction on the GPU as long as the lifetime is constant.
If you wish to do something more complicated than a linear time-based fade you have a few options. The simplest would be to spawn a blueprint that uses a timeline to drive your material parameter. You could also use time as an input to a texture sample, effectively creating a lookup texture.