Thanks for your feedback.
I absolutely cannot reproduce this. The taxonomy is added with WordPress standards and with the recommended hooks/ filters from the WPDR base plugin developer.
There is no timeout setting in place in my plugin - and I really don't know of any in the base plugin.
Where does this long time waiting occur?
When adding a file and then use the checkbox for adding a category, or in the same process adding a new category?
When adding a category on "standalone" category admin pages takes it also so long?
Is it also when using/adding categories for regular posts or only for this 'document' post type?
When it happens on the download/document edit screen than it could be an Ajax issue with your install: make sure the PHP memory limit is at least 64M, better use 96M or 128M ---> please make sure an addition in your wp-config.php file also processed and not blocked by your hosting company. Some hosting companies have internal blocking in place, for example "1and1".
Also, in general there can always be plugin conflicts that do something with Ajax in the admin or do other things with taxonomies etc.
Thanks, Dave :)