Modern Team Site - Global navigation

I'm a crossroads with this.

I've created a site for one workgroup, and several others would like the same site. They can't share the same information, so I have to duplicate my effort. I don't mind the work, but when I went to set one up today, I had to create a site as a modern site/group (that's okay) but since my pages use 'legacy' web parts,  have to create wiki pages.

While I'm okay with the sidebar collapsable navigation, it doesn't carry over to the legacy wiki pages. (Those links cannot be collapsed).

In my use case, sales managers want to access information on 40 different products and be able to quickly navigate between then based on what the customer asks for. It must also be easy for end users to manage the navigation as they add additional products. Any ideas?