There are a couple of ways to view the previous 1 on 1 notes you've had with your direct reports. You can use the 1 on 1 Timeline within the 1 on 1 modal, as well as the 1 on 1 preparation section, or the 1 on 1 Details report in Insights.
1 on 1 Activity History
The Activity History Tab gives you an overview of how many 1 on 1's you've given over a 12 week period of time for each direct report. Each dot you hover over will display the 1 on 1 information (date, agendas, priorities, and notes).
1 on 1 Preparation
When preparing for the next 1 on 1 meeting you will have, on the right-hand side a display the previous 1 on 1 notes, priorities, and agenda items that you can choose to add to the upcoming meeting. For 1 on 1 history click the 'History' tab and there'll be an option to head to previous 1 on 1 history. Your direct report can head through this history as well!
1 on 1 Details Report
The 1 on 1 details report is located in Insights > Manager > Meeting Details Report. This will display all 1 on 1 meetings you've had with your direct reports over the date you've filtered for. It gives you durations, agenda count, meeting date, and more. You can select the view option to view each meeting that will display all the information as well as download a report.