This simple, turn key Google Sheets add on makes it easy to add time staped commentary to your Google Data Studio dashboard. It creates a new spread sheet formatted for Data Studio. 

It then populates the "date" column with a date/time stamp when you add commentary and the number of the comment. Once this sheet is linked to your Data Studio Dashboard you can filter by date and get relevant commentary in a Data Studio table. 

With some simple changes to the table, described in the app, you can include only the date and the number of the comment. You can edit both of these in the sheet if you want