The Dictionaries tab is used to select the dictionaries used during execution:

By default, the Use default dictionaries checkbox is checked. The user may wish to add or remove dictionaries from the default list.

The field on the left contains a list of groups of dictionaries. The groups are marked either with a green checkmark or a green square sign. The checkmark indicates that all the dictionaries of this group are used by default. The square sign means that only some of the dictionaries in the group are used by default.

If you uncheck the option Use default dictionaries, you can select and deselect both whole groups of dictionaries and individual dictionaries.