Conference 2020 authors who have already submitted a presentation proposal AND who need to edit those proposals, can easily do so within the Conference 2020 Call for Papers submission portal.
The Conference 2020 Call for Papers system can be accessed directly from the ISAAC website here.
When you access the home page of the Call for Papers system, you will see the home screen as per the image below:
Simply click the "Edit Submission" hyperlink. You will need your submission id number along with the password that was set when the proposal was first created, in order to edit the proposal.