How to display specific posts on different pages in sidebar (WP as CMS)

I am creating a WP site, and what I need is to have about 30 sidebar module items that are conditionally displayed in the sidebar. I have created them as posts, but could change that if needed.

The issue is that I need the client to be able to say include modules(posts) 1,2 & 5 (preferably at the page level) on one page, and different ones on another page. I have tried every plugin that I could find, I have tried doing it via categories, custom fields, tags etc. but I just can’t figure it out.

I’m sure someone else smarter than me has figured this out.

I would really appreciate the help!!!