The activity log helps you determine what events happened on a specific proposal. This shows you when a proposal has been viewed, updated, etc.
You may also add a reminder here for yourself (internal) just in case you need to follow up with the customer or remind yourself of any other task related to that customer or proposal
Setting a Reminder from the Activity Log
Select your proposal from the proposal list view
Then, go to the "Activity Log" which is located on the top-right corner of the proposal after you click into it
From the same corner, click the "+ Icon"
Populate the description to add the content of your reminder
Check the "Add Reminder" tick box
Select the date for this reminder
Hit "Create"
This will send you a reminder email notification just as an accepted or sent proposal would.