How to get there: Click All Posts in the sidebar → open the filter sidebar on the left → scroll to the Custom Fields section.
If you've defined custom fields on your post types (such as Browser, Severity scope, or Reported by on a Bug Report post type), you can filter the admin All Posts list by those field values, the same way you'd filter by status or category.
For setting custom fields up in the first place, see Set up post types and custom fields.
The list re-filters as soon as the row is complete. Multiple rows AND together, so you can chain conditions like "Browser contains Chrome AND Severity equals critical".
Click the x at the end of any filter row to drop it. The list re-filters immediately.
The filter looks at the raw custom field value, not the post type. A post only matches a row if it actually has that custom field attached (which means its post type defines it). Posts of unrelated post types are silently excluded, which is usually what you want.
Custom field filter combinations can be saved as a query like any other filter. See Saved queries and filters.