Starting from 2.7 b138, you will be able to add a new filter to the sidebar called "Custom Search".

Custom Search filter device

This filter will behave much like the "Search All" filter, but it will allow you to choose which fields to search rather than all the fields.

You can choose which fields to search from the "Fields to search" menu, accessible from the filter device tools menu (by clicking the down pointing triangle).

Note: This filter will return rows that contain the search text in any of the selected fields. If you want the rows containing the search text in all the selected fields, you will have to use per-column filters.