The Category list is the single source of truth, shared by the Playbook metadata and the Table of Contents.
### Monday plan
* Create a SharePoint list named Categories. One item per Category, using the Title column for the Category name.
* Configure the Documents library's Category column as a Lookup column pointing to `Categories → Title`, rather than maintaining a separate Choice list.
* Create the Browse Playbooks base view, preserving the existing card formatting, descriptions and Severity pills.
* Build the ToC from the Categories list, using a List web part on the landing page.
* Assign a filtered-view URL to each Category, pointing to Browse Playbooks and filtering on the selected Category.
* Use the same Categories list for both purposes, so Category names are maintained in one place.
### Architecture
Categories (SharePoint List)
19 category records · Single source of truth
Documents library
Category lookup column
Playbook ToC
Category links
Browse Playbooks
One formatted view · Filtered by selected Category
One technical detail: SharePoint Lookup columns store an item ID behind the displayed Category name. Filtering may therefore need `FilterLookupId1=1` with the corresponding `FilterValue1`, rather than filtering as a plain text field.
The Category list can also store a URL column for each ToC destination. That gives you centrally maintained navigation links without manually editing the landing page for every Category change.
This is the architecture I should have carried forward.