Hello, when narrowing down my Search, Wadena County is not listed within Minnesota options using the Filters. Please add.
The fact that it doesn't appear as a filter indicates that none of your search results were classified as Wadena County. If you do a different search that does include records from there, then the filter will appear.
If you look in the catalog, Wadena County has it's own collections. What are you looking for? There are birth and death records from 1880, marriage records from 1873, probate, naturalization, land etc records there as well.
Catalog Search Results for United States, Minnesota, Wadena - FamilySearch.org
Also, what year were you searching for records? The county was created in 1858 so may not have records from before that time. The records prior to that could be in the collections of what ever counties it was created from. That could be why the filters are not showing any Wadena options.