You can put an Opportunity On Hold from any stage in the Sales Workflow. Putting an opportuntiy on hold will help to visually 'grey out' that opportunity. Additionally, it is connected to a default Quick Filter tile that can easily by used to view or remove any opportunity on hold.
To put an Opportunity On Hold, select the opportunity tile, and click the Selected Opportunity drop down at the top of the screen. Select the Put On-Hold option in the drop down. You can also put multiple items from the workflow On Hold, by selecting multiple items on the workflow and repeating the above steps.
Once you've made your selection(s), you'll see that opportunity in your sales workflow lightly grayed. You may also then utilize the filter to display only those opportunities that are on hold.
Take a look at content to help continue your learning of Crelate's Sales/CRM functionality.