Everything is in Google Ads, under Experiment (A/B testing): open Edit on a Search or Display campaign › Experiment (A/B testing). Google copies the campaign, changes the copy (bid strategy or landing page) and splits the traffic (from 10% to 90%). The modal shows control and test, the variation and the statistical confidence. At 95% or higher, you decide: Apply moves the change to the original campaign, End discards it. Campaigns with a shared budget aren't supported.

Dates: Edit on the campaign › Dates. For several campaigns, select them and use Edit campaigns › Dates. The end date can be any date from today onward (or none). The start date can only be changed before the campaign starts running.

Labels: select campaigns, ad groups or ads and use Edit campaigns (or Edit groups, Edit ads) › Labels to apply or remove labels. The Labels button in the bar filters the list.