System Information
Operating system: Windows-10-10.0.17134 64 Bits
Graphics card: Intel(R) HD Graphics 4400 Intel 4.3.0 - Build 20.19.15.4549

Blender Version
Broken: version: 2.80 (sub 74), branch: master, commit date: 2019-07-09 22:45, hash: rB3b4054cb586f
Worked: (optional)

Short description of error
· The option of being able to change the "control edge" with the keyboard shortcut "Alt + Wheel mouse" doesn't work during the execution of any tool that slides vertices or edges with the option "(E)even" active (for example, in the tools: "Slide Vertices Shift+V", or "Edge Slide", or "Loop Cut & Slide Ctrl+R", or with the generic shotcut for slide G+G).
· This shortcut (Alt+Wheel mouse) always existed and always worked in version 2.79 and earlier of Blender, and it is very useful for achieve that the shape of the sliding loop has more or less travel according to the chosen "control edge", but this shortcut doesn't work now in Blender 2.80. This shortcut does't work in spite of the fact that the User Manual of version 2.80 continues to reflect it in its explanations as it did in the manual of version 2.79:
https://docs.blender.org/manual/en/dev/modeling/meshes/editing/edges.html#edge-slide

Exact steps for others to reproduce the error
In Blender v 2.79 it works, as shown in the following image:

… In Blender 2.80, simply doesn't work the shortcut "Alt+Wheel mouse" with the option "Even" active, when trying to change the "edge control" to make the sliding of the loop on it.