Smart previews in Lightroom CC?

Hi! I'm a wedding photographer and so I'm used to using Lightroom to manage thousands of pictures at once, cull quickly, etc. All is fine now on Lightroom Classic CC, but I'm considering jumping to the new Lightroom CC for its ability to sync with mobile; I like the idea of being able to cull more while I'm on the go and do my editing there as well. However with Lightroom CC, both on desktop and on mobile, I can't locate the option to build previews for photos, either standard or smart previews. I always build them in advance on Classic so culling moves so much more quickly, but on the new CC I have to sit and wait for each image to load for a few seconds while flipping between them, which is dramatically slowing me down and frankly not helping my motivation. Is there a button to build standard previews on both desktop and mobile that I haven't been able to find, or is it not an option?

Edit to update my question: Or, how do I just sync smart previews from Classic into CC to save space?