How does the Frequently Used Actions feature function in Vault?
For documents, actions are tracked per user, document type, and lifecycle state. Object record actions are tracked per user, object, object type, and lifecycle (state). Each click on an action is tracked regardless of whether the action succeeds. Bulk actions are not tracked. A running total is kept for each action of how many times it has been taken.
The four actions taken the most number of times are displayed in the action bar. Actions that are not available on a particular record to the current user because of permission or record state context are hidden (not displayed).
Initially, default actions are placed on the Action Bar. Once an action has at least three uses it is eligible to replace the actions currently on the action bar. Actions must have been used three more times than the least used action currently displayed in order to replace it on the action bar. This is to stop two actions that are each used around the same number of times from constantly replacing each other.
When an action has not been used for three months the collected data on it will be deleted. So if the action starts to get used again in the future, data will be tracked from that point onward.
Vault Documentation: Vault Help