You can create many rules to form a full set of rules, and then apply multiple rules to categories and folders.
When you select the Manage Rules action for a category/folder with defined rules, the Rules page is split into two.
The left side of the page lists the rules that make up the rule set. If the category/folder inherits rules from a parent category/folder, those rules appear here too. The rules run in the order they're listed. Inherited rules are always run first.
A check mark to the left of the rule means it's active.
Selecting an individual rule in this list displays its details on the right side of the page.
On the New Rule page you can add a new rule to a set of rules in exactly the same way as the first time you created a rule, see creating a rule [7].
If a category/folder has inherited rules these are displayed on the left side of the page.
Any inherited rules are switched off for the category/folder and Don't Inherit Rules is shown. You can click Don't Inherit Rules to switch inherited rules back on for the category/folder.
If you might want to use the rule again, consider disabling it instead. Edit the rule to do that.
Links:
[1] https://docs.alfresco.com/../tasks/rm-rules-new.html
[2] https://docs.alfresco.com/../tasks/rm-rules-edit.html
[3] https://docs.alfresco.com/../tasks/rm-rules-reorder.html
[4] https://docs.alfresco.com/../tasks/rm-rules-inherited.html
[5] https://docs.alfresco.com/../tasks/rm-rules-delete.html
[6] https://docs.alfresco.com/../concepts/rm-rules.html
[7] https://docs.alfresco.com/rm-rules-define-create.html
[8] https://docs.alfresco.com/../concepts/rm-rules-defined.html