Hi @MJ3000 Welcome to the forum.
The issue here is ‘Auto Voice Leading’ is a one off function only available once multiple chords are selected. It is not a Voice Grouping profile or Extraction - I can certainly see the confusion here.
You can right click a chord and ‘Extract Vocicing’ (to get the slash voicing), then simply click ‘Extracted Voicing’ on the target Motion clip (in this instance I only applied it on the Motion I wanted to have the same slash chord as the Chord track).
That should do it. See attached.