Hey Alangreg,
first of all, thank you for choosing Ikebana!
There is a section called “Post layout” in the right-hand side of the editor view for each project, which allows you to control whether or not a particular project has a sidebar; if that one doesn’t show by default, please click on the “Screen Options” tab in the top right corner of the editor view and tick the respective box.
If you need each project to have unique content in the sidebar, you can use the theme’s built-in custom sidebar functionality; new sidebars can be created in the “Appearance -> Custom Sidebars” admin section, filled with widgets in the “Appearance -> Widgets” section, and assigned to a specific project by using the “Sidebar” settings box in the right-hand side of the editor view for that project.
Please let me know if you face any difficulties with this one, or in case I misunderstood the question :)
Sincerely,
Andrii / Satori Studio