Undefined index: cb

I can’t duplicate the issue here.

The index this message is referring to (‘cb’) is the one used to identify the checkbox column in the term list. It is core WordPress. This array looks like this, code-wise:

[28-Mar-2017 23:10:47 UTC] Array
(
    [cb] => <input type="checkbox" />
    [name] => Name
    [description] => Description
    [slug] => Slug
    [posts] => Count
)

If you are seeing this message, the ‘cb’ column has been removed by another plugin or setting somewhere in a theme.

Please try again, with only this plugin and the twentyseventeen theme active and see if you have the same results. If you do, please edit the file referenced on line 244 to add the following:

error_log( print_r($columns, true));

Then revisit the steps to generate the error and check your log to see the contents of the array, and copy them into this thread.

Closing.