Here's one way I am using this plugin. After configuring it to store reading locations (four custom columns; koboreadpct integer, koborating integer, kobolastread date, and koboreadloc, text and associating them with the corresponding fields in the plugin setup), I added a new custom column
Column Heading: Finished
Column Type: Column built from other columns
and then added the field #finished to my shelf definitions which now read
#myshelves, #finished, series
This has the effect of when I update the reading stats (I find the easiest way for ME at least) is to sort the Library view by the On Device field, select all the books shown as being on the Kobo and then select the plugin's option to store reading location, the Finished column gets set to the word Finished for all books at 100% read.
The next time I attach the device and the automatic metadata management runs, all the books I have finished now appear on a new shelf Finished.