We don't currently have an option to reset the bar statatistics, however this can still be achieved by cloning your bar and deleting the original.
Clone the bar you wish to reset the stats for. This will automatically be added to "Inactive Bars".
Delete the original bar that you want to reset the stats for or make it inactive.
Go to the "Inactive Bars" tab and activate the cloned bar.
The cloned bar will now appear in the "Active Bars" tab with the stats set to zero.