I haven't found any documentation yet other than the help file.
to exclude 50 and 70 you can enter -50 -70. If you wanted to exclued a negative value you could use -"-40". As far as I know there's no way to enter a search string for <> *qlik*. For <> other* you can enter -other. For <> *qlik* you'll have to open the advanced search dialog (ctrl+shift+f) and enter an expression like =count({1-<MyField={'*qlik*'}>}1)>0