The only way I figured out to do it is to go into widget.php in the plugin directory.
On line 142 it uses the get_terms function, so you can alter the term list however you like.
To exclude a specific category, just change that line to:
return get_terms( $tax, array('exclude' => 4)); // change 4 to whatever category id you want removed
Hope that helps.
it works only with one category.
how can I manage this with excluding more than one category ?
I tried it that way,
'exclude' => 5,
'exclude' => 12,
`
but it doesn´t work.
who can help?
The easiest way to do that is to just do:
'exclude' => '5,12'
You can exclude how ever many you like just by using a string of comma-separated id’s. Talks about it in the get_terms reference.
Hope that helps.