Unlike Quickbooks Desktop, Quickbooks Online timesheets don't have Payroll Codes - the items that dictate OT and rate of pay. Pay rates must be manually calculated outside the timesheet when you are preparing each employee's paycheque. Because of this, LMN cannot export OT or payroll code information to Quickbooks Online timesheets. (You can do this with Quickbooks Desktop, just not Quickbooks Online)
Quickbooks Online had released some news earlier in 2016 that payroll items would be available on QBO timesheets approximately mid-year 2016. At the time of this article, that feature has not yet been released/added to QBO.
If you'd like to request this feature be added to QB Online, or get an update on their progress, you can contact them at their support site: https://community.intuit.com/quickbooks-online