Internal Loop-point Automation
Despite initial appearances, Grace's sample markers and loop points can all be automated.
1) Select a modulation slot at the bottom of the GUI.
2) Hold ALT + drag the loop start or loop end marker. You'll notice a shaded area extend away from the marker. That marker is now automated!
It's entirely not intuitive to discover during general use. I need to add some visual cues.
External Loop-point Automation
The sampler markers can't be automated directly via MIDI. Instead, automate the XY pads from your host, then link the XY pads to the loop markers.