[anthony.burton4]

Can't use Search & Replace for this operation as the field does not appear in the list.

I'll repeat the scenario to avoid confusion.

I have 2 books, one marked with 5 stars, one with 2 stars.

I select both the books and open up the bulk edit screen.

The custom field I want to reset is currently displaying "unrated".
Attempt#1: I check the "Apply changes" checkbox next to this field and click Apply.
The data is unchanged.
Attempt#2: I set the field to 0 stars and check the "Apply changes" box and click apply.
The data is unchanged.

Anyway - I've found a workaround now - should have spotted this before.
If I set both books to 1 star and click apply, and then set it to unrated and click apply, the field is successfully set to unrated. I just can't go directly from a mixed result set to unrated for some reason...

Note a similar thing happens with text based custom fields too - however I use the search and replace with a "(.*)" regex expression to empty them so I've worked around the problem.

Using calibre 64 bit 0.9.16