When the Custom option is selected, the search slider will appear on the right hand side. You can find out more about each individual search option in User Guide - Search for items.
The Cypher search option isnot available by default and can
enabled for users with the default SUPER ADMIN and ADMIN roles. If you would like to enable it for other users, either modify an existing role to enable the Cypher Search or create a new role specifically for that - see Admin Center - Roles panel:
You need to enable at a minimum the READ and CREATE permissions to perform a query. The Cypher language is powerful and enabling the UPDATE and DELETE permissions will allow users to perform cypher queries which can update or delete existing application data.
Removing objects from a custom scope
Starting 2.5.x, it is possible to remove objects from a custom view using the right click Remove object(s) option (you can also use the DELETE key):