
Throw Books away
The above with a custom column (I chose date type) as the filter trigger
Have Read:
Code:
#finished:true and formats:True
I have formats:true because I keep empty books as a wish list or link to a compilation containing YMMV
To Read:
Code:
#finished:false and (formats:EPUB or formats:Mobi or formats:AZW3)
(I have both a Kindle and a Kobo, so different formats are checked as well as filter out wish list)

In addition, I have OTHER search filters that use this read status.
Code:
Dates: 2000 are 'abandoned', 1999 have been split
I use EPUB Split plugin to make a big monster (boxed set) into a kitten sized read