A Label Color Presets row under Label Defaults picks the 16 label names
and colours from a preset. The dropdown lists the built-in "Default"
(the labels FilmCraft ships with) and the presets in the Label Presets
folder beside the preferences, and reads "<name> (Modified)" once the
labels differ from the chosen preset. Icon buttons: Revert (back to the
preset's colours and names), Import (copies a preset file into the
folder and selects it), Export (saves the dialog's labels to a file
named as the preset), Show Folder, and Delete (user presets only).
Choosing a preset or reverting applies on OK like the other fields;
Cancel discards it.
Presets are small JSON files: a name and 16 labels, each a name and a
labels, names trimmed and at most 64 characters, valid colours); a bad
file shows its error in the dialog and changes nothing. The same is
reachable as labels.presets, labels.importPreset, labels.exportPreset
and labels.deletePreset, with the selection stored as labels.preset.