Hello Bharath and David,
thanks for your feedback,
and sorry for not being clear enough.
In BEx's design mode you can filter on the dimensions available for drag&drop in the filter panel.
Here, for instance only three (out of +50 free navigation dimensions set in the query) will appear:
This allows the workbook designer to offer the end-user a restricted list of dimensions in the left filter panel. Idea behind is that the user is not directly confronted with too many free navigation possibilities which might confuse him.