Activity
Activity under Users & Access is the panel-wide audit log: every admin-side action, who performed it, from which IP, and when. It works exactly like the server activity page, searchable and paginated, with an Actor column (including "Impersonated by ..." markers and System rows for actions without a user), Event, IP, and When, plus an info button on rows carrying extra JSON metadata. Click an actor to filter the log to that user; Clear User Filter undoes it.

Events are namespaced by the admin resource they touch, which makes searching easy:
settings:update user:create role:update
server:create oauth-provider:update node:allocation.create
location:create nest:create egg-configuration:update
Per-account activity lives on each user's Activity tab, and per-server activity on each server's Activity page.
INFO
Admin activity is pruned automatically, by default after 180 days. Both the retention days and an optional cap on the number of entries kept are configured under Settings > Activity.