Go to Market Pro Max –> Optimizer
On the table that lists all of the conversions tests that you have setup, on the right hand side you will see a blue, yellow and red box. The boxes have the letters P, C and X in them.
The P box will let you pause the currently running conversion test (this leaves out the variation page).
The C box will let you clear the data of currently running conversion test (this resets everything to zero).
The X box will let you delete the currently running conversion test.