How do I save the current positions of all EmEditor windows, and open all the windows at the same positions next time?

Left click on the Tray Icon to display the Tray Icon menu, and select the Save Workspace command to save file names and cursor positions of the current workspace. Next time you can select the Restore Workspace command to restore the previously saved windows with the same file name and cursor positions.

You can also use the Save Workspace and Close All command to close all windows after saving the workspace, or use the Save Workspace, Save, and Close All command to save and close all windows after saving the workspace.