Table of contents:

Active timers for a user

All issues with an active timer for a given user are listed on the user Profile page in "Active Issues" tab (as presented on the screenshot below):

The same set of issues can be listed on JIRA Search page with JQL. Read below for more details.

Active timers for a project

All issues with an active timer in given project are listed on the project Summary page in "Active Issues" tab (as presented on the screenshot below):

JQL support

Active issues can be also searched with JQL. That method gives comprehensive and flexible search capabilities.