I was looking over the User Guide on filtering Time and Cost reports, 
https://www.openproject.org/docs/user-guide/time-and-costs/reporting/#filter-cost-reports

but I cannot seem to find documentation on the TYPE of filters, i.e., 
• DOESN'T CONTAIN 
• CONTAINS
• IS 
• IS NOT 

do any of these filters allow for a wild card? 

I was looking to do something like [FieldName] CONTAINS [A-Z] to filter work packages that only have a value in a particular field (i.e., not blank or empty). 
I tried doesn't contain with a blank (space), i.e. " " without the quotes, which did seem to work, but it would be nice to have some documentation showing examples of each type of filter with an explaination.