Then this add-on allows:
To Adds a widget to a thread that displays members who are currently viewing the thread.
You can edit position in:Your Forum > Admin > Appearance > Widgets > Thread view: Below messages > Thread viewers.
If you want you can add manually widget:
You can edit position in:Your Forum > Admin > Appearance > Widgets > Thread view: Below messages > Thread viewers.
If you want you can add manually widget: