There's an option to horizontally align fields (i.e. left, right and centre) but not an option to anchor text to the top of a cell. Do I need to write custom CSS for this?
Custom CSS seems to be your best bet here. I tested out a couple options and it seems like selecting the innermost cell-container and then applying these styles:
Just as a note: custom CSS is now written in the three dot menu > "Scripts and Styles" > CSS. I just wrote it in the old style (in a text component) to be able to show everything in 1 screenshot.
Let me know how this works for you!