To search for attributes and audiences in the crosstabs builder, click on create a crosstab:
Then select add an attribute/ audience:
From there you, can search to find any attributes or audiences you want to use in your crosstab. You can sort results by relevance or alphabetically. Search not only finds all matches for your exact search term, but also includes suggested categories:
With the filters toggle on, your search and browse results will only include attributes that are compatible with the waves and locations you have applied: