I'm trying to set up a customized column view in EMDM explorer but it won't allow me to to add a column for "Checked Out By"...been getting an error that says this variable is only available for search results and BOMs. However there is a check out by column in the default view so it should be possible. Any ideas?
You have almost answered your own question...
There are Default columns and these cannot be removed or added again. You can only add extra columns and by default they are added after (to the right of) the Default columns with all users needing to manually re-order them.