Slope Storage is a glitch related to Speed Restoration, where Ammy's grounded vertical velocity is also stored when she jumps. If you jump while dashing up a steep slope, the next time Ammy begins dashing (via restoration), she will do a small jump, as though going over an invisible bump in the floor. This bump tends to be no taller than Ammy herself, but it's height will be smaller if the slope was shallow, or if Ammy didn't have full speed (i.e. gold dash) when jumping on the slope.
During the bump, Ammy will retain her grounded state unless (seemingly) she gets too far from the ground, at which point she will become airborne with no jump, as though she'd walked off an edge.
The stored upward momentum is lost after being used once. It is also lost if stored dash is lost (e.g. if Ammy walks). This means that, to transport a stored dash over a long distance, you have to use tackle jumps.
Due to the various limitations of Slope Storage, there are currently no known applications of it in speedruns. The only trick which requires Slope Storage is getting the Kamiki Sun Fragment without Water Lily or double jump. The concept of using Slope Storage to perform an Air Ground Tackle over the low invisible walls that typically surround platforms will likely be key if a real use for Slope Storage is ever found.