When editing shapes, you cannot add new vertices, just edit/delete the existing ones.
Addition of new vertices will work properly in v3.14. The minimum step between the vertices will be 0.5px. The usage of this new functionality is demonstrated in this video: https://community.icons8.com/uploads/default/original/1X/2a59b73602236dfb947022ef951883998eb3a5ff.mp4
Perfect. Thank you for the reply. All my best!