Locate C:\Users\USERNAME\Documents\Mirrors Edge Catalyst\settings
Open PROF_SAVE_profile with a text editor
Add:
GstKeyBinding.default.ConceptMouseBack.0.axis 24
GstKeyBinding.default.ConceptMouseBack.0.button 0
to activate mouse back
GstKeyBinding.default.ConceptMouseForward.0.axis 24
GstKeyBinding.default.ConceptMouseForward.0.button 0
to activate mouse forward
Now, go into the game and configure your controls.
Mouse back/forward will not be displayed in the game (because its not implemented in the game)
example: select "heavy attack" then bind it to key 2, click "heavy attack" again and press mouse back.
Now you have bound "heavy attack" to key 2 and mouse back
Good luck!