I noticed a discrepancy in the action strings documented for ROR and the official Elasticsearch documentation for SLM, and I was wondering which one I should be using on my cluster.
Xpack Security and ROR are both security solutions. When you use one, you don’t need the other.
The security privileges are related to Xpack Security only. ROR doesn’t use them.
However, each Elasticsearch API request has an action assigned. You can find the list of all available actions in the link you showed. And you can restrict access to some actions (eg. cluster:admin/slm* /notice the wildcard in the action name) using the actions rule.