You can now see a timeline of when various actions were taken on a document , for example when it was sent, when you received/recorded a payment on the document, when it was approved, etc. The document timeline is currently available for proposals, invoices, and retainers. 

To see your document's timeline, click to open the proposal, invoice,  or retainer and then click the button with three dots to the right of the "Edit" button in the top right corner of the page, then select "View Document's Timeline" and you'll see a panel pop out from the right side of the screen with the document's timeline: