Bug: Currently deepcat works in search, but not in advanced search.
At the moment you can use this as a workaround if you want to use the advanced search.
- enter the required search string into the 'normal' search field
- execute DeepCat search by clicking the Search button or pressing the Enter key
- switch to the advanced search and add the needed modifiers ( you will see now a search string like incategory:id:5390661|id:8473665 )
- re-execute the search in the advanced mode