To complement the keyword implementation, the logic of combining keyword presets has changed in Capture One to allow blending of presets in a more predictable sequence.
Tools affected are keywords and IPTC fields where word lists are supported:
In the versions before Capture One 9, for example, combining the presets
would result in B and C being removed in the keyword list.
Capture One now combines the list in a more logical way, so that the resulting list would be: