[PeterT]

The columns are used to store info. retrieved from the Kobo (and to let you restore it to the Kobo as well).

I created 4 custom columns for use by david's utility plugin:

Spoiler:

Lookup Name: koboreadpct
Column Heading: Kobo Read Percentage
Column Type: Integers

Lookup Name: koborating
Column Heading: Kobo Rating
Column Type: Integers

Lookup Name: kobolastread
Column Heading: Kobo Last Read TimeStamp
Column Type: Date

Lookup Name: koboreadloc
Column Heading: Kobo Reading Location
Column Type: Text, column shown in tag browser

I created my "custom" column

Spoiler:

Lookup Name: readstatus
Column Heading: Reading Status
Column Type: Column, built from other columns
Template: {#koboreadpct:'cmp($, 100, cmp($, 0, '', '', 'Reading'), 'Finished', '')'}
Sort/Search column by Text

I then restarted calibre (required after column changes) and configured the driver

Spoiler:

Current Reading Location Column: #koboreadloc
Percent Read Column: #koboreadpct
Rating Column: #koborating
Last Read Column: #kobolastread

Strictly speaking I'm ONLY using the value of #koboreadpct so don't really need any of the other columns.

Finally I added the value #readstatus to the shelf value in the Kobo device driver (or the Kobo Extended device driver).

One final restart of calibre for safety and all is done.