How do i delete multiple time activity entries at once?

Use a deleer tool

https://get.transactionpro.com/qbo

I can share some information about deleting time activities, @stephdionne-slee.

At this time, you can delete your time activity one by one. You can do it by clicking the trash icon on your timesheet in QuickBooks Online. 

For more details, you can read this article: Turn on and set up time tracking in QuickBooks Online. I'll show you how to check time details, track and manage time, and access Time Tracking reports. 

In the meantime, I'm adding this article to further guide you in managing your workers' and employees' time using QBO: Track and manage QuickBooks Time in QuickBooks Online. It includes topics about viewing, adding, editing entering and approving timesheets. 

I'd be glad to answer any future questions you have about deleting timesheets. I'm just around to help. Take care always.