As some of you may have already discovered, lock and spread is not supported in the New UX, only classic. 

https://community.anaplan.com/t5/Idea-Exchange/Hold-and-Release-functionality/idi-p/77486

@sandeep_bk posted this idea back in July but it hasn't gotten much attention. This is a pretty important feature for retail and supply chain in general so I hope you'll consider giving it an upvote!