This Ableton tutorial walks through the Expression View, the dedicated tab in Live's Detail View where recorded MPE data lives and can be edited note by note. Clicking any note gives immediate access to its breakpoints for pitch, slide, and pressure, and you can drag them to simplify the curve, double-click to add new ones, or hold Cmd/Ctrl to snap them to the clip's grid.
Because MPE data is stored per note, each note's slide and pressure curves are fully independent and editable the same way you'd edit any automation or modulation curve in Live. Notably, you don't need an MPE controller to work this way — the Expression View is available for any note in any MIDI clip, so you can draw and refine MPE data entirely by hand. If you record with Capture, all MPE data is retained alongside the notes.