Where can I find the information entered by customers completing forms within project tasks?

To view all custom form submissions, navigate to the following:  From the left hand main menu click on Settings < Custom Forms.  Next, click on the 3 dots next to the custom form that you'd like to view all customer submitted data, and select 'View Submissions'.   

Once you click 'View Submissions' you will see a table of all form questions (as column headers) with each of the customer responses below in line with their row.  There will also be a 'submission date' column which denotes the date and time the form was submitted.  You can click into the column headers to edit/add/remove any columns, or sort as appropriate.  Lastly, you can click the 'Export' button in the top right corner to export all of the custom form customer submissions into a csv / spreadsheet file.