If you want to customize something, you start with the tabs of the dialog, e.g. with "Menu". Next step is to narrow the selection, e.g. to "Help". I expect the tool to narrow my selection just below the tab. But it is far away in a different column. In addition, it has no label.
Created attachment 136051 [details]
old vs new Customize dialog (Writer)
In general I'm OK with the revised dialog but some usability issues with the new layout.
Some labeling is missing--and the unfiltered megalist of functions on the left is a bit daunting. There is no guidance (other than descriptions) as to which controls are reasonable additions to the default configurations.
Search was always on top and should be there. The original proposal  was to use a tree instead of the flattened lists without the 'Category' filter. This idea was rejected because of simpler controls and less implementation effort. So it's a WF, unfortunately.