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Horus68 - I have all the non long-text columns displayed in two columns at the top of the default Custom columns tab, the long text columns are shown under that, again in two columns - viz:
I don't recall doing anything to force that 2 column layout -- other than selecting
Default in
Edit metadata (single) layout:.
Hopefully someone will know why there is a difference.
BTW: that's my Test library, but my other libraries are the same.
But, because I edit metadata in the Book List using F2, none of that bothers me as I rarely go into Single Metadata Edit. For long text HTML custom columns I use a Column icon with No Text, viz:
I much prefer 'spreadsheet like' interfaces to 'form filling' dialogues. I use the View Manager plugin to create different Book List "Views" (sort order and column sequence) for each library . e.g for Normal use and Data Entry use.
Added: I am using Windows 10 Pro 1903, Calibre 4.4
BR