How to Create a Steam Workshop Collection
1. Go to steam workshop.
2. Go to browse > Collections.

3. Click on Create Collection.

4. Fill out the form & Click Save and continue
5. Add a Background image.
6. On any mod you wish to add to this collection, Click Add To Collection

7. Back on the main workshop page Go to browse Subscribed items.
8. Click Collections > Items.
9. Click your Collection.