In Webtrekk it is possible to create filters that contain the predicate "not equal" and the wildcard "*":
Unfortunately, using such a filter is not reasonable because combining "not equal" and "*" excludes all results that were measured. Consequently, such a filter does not yield the desired result, regardless of the used dimensions, scopes and of using "which contain" or "which do not contain".
If you created such a filter, in many cases you probably will have the following use case in mind:
Show analysis data for visits in which for a specific dimension, no values were tracked; e.g., for visits in which no search engine was used.
You can realize this use case by negating the whole container (i.e., by using "which do not contain" instead of "which contain").
Further information on how to use filters can be found in the training chapter on User Interface 1.2 – Segmentation and Filter Options.