Currently, the Approve button of Salesforce is displayed on the Home Page of CRM Online when the Approve Component is enabled for the Home Page. Is it possible to hide the button or the Action column?
Users should use the Approve button of Event Management to initiate the approval workflow. Do not use the Approve button that is provided by Salesforce when integrating the Event Management feature with the Approval Workflows of Salesforce.
The Approve Component is a standard out-of-box item. Salesforce does not provide the ability to define the columns just like all other related lists or views. Users can build their own Approve Component using Visualforce.
CRM Help Documentation: Approval Flows Integration
Salesforce Documentation: Ability to customize the columns in the Items to Approve section on home page