Hello and welcome to the Community, DJL Fab
Currently, it is only possible to have one cost rate per employee at a time on the Projects feature in QuickBooks Online.
We can see how this would be beneficial for your business and recommend submitting feedback to our Product team by selecting the Gear > Feedback in your account.
Thanks for reaching Intuit QuicBooks for support on the Community today. If you have any further queries, please get back in touch.