Prepping recipes ahead of time
Prep ahead for a later meal, like an overnight dough, at a meal you are already cooking, so kitchen time is grouped into fewer sessions.
Work you prep ahead for a later meal, like an overnight dough or a chicken marinade, is incorporated into the meal you are already cooking, grouping kitchen time into fewer sessions.
Which recipes are prepped ahead

Mise en Party's Prep ahead feature identifies recipes with long rests of an hour or more, such as overnight marinades or breads, and breaks them into separate parts which can be individually planned. When a recipe with a long break is scheduled, the work before each long rest is pulled out into its own row and can be scheduled like any other recipe. This lets you prepare a dough for tomorrow during the downtime of tonight's cooking, reducing your number of kitchen sessions.
On a recipe's page, the timeline at the top shows each part in order, with the rest between them, ending at the time the recipe is served. Drag the slider under a part to lengthen or shorten the rest that follows it, within the range the recipe allows; the part's start time moves with it, so you can see when to start each part to serve on time.
Where the parts are scheduled

The schedule will automatically try to place the prep into an adjacent meal within the required rest time. If you have nothing planned but prep work, you'll still need to do the prep work; it'll just be its own little meal, called Prep, that will show up in the schedule to remind you.
How to move a part to another meal
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On the plan, find the part's row, named for the recipe and its part, like Overnight Focaccia · part 1. A part of a dish can also be found by expanding the drop-down on that dish's row in the plan.

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Drag the row onto a different course, or click the ▾ chip under it and pick the meal and course.
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If the new meal is too close to or too far from the rest of the recipe, the row is marked with how much rest it gets and the range it needs, like rest 1h, needs 3h–4h.

Room temperature and soaking
Like thawing, some recipes call for items to be at room temperature or soaked overnight. The recipe's author marks these, and they appear on the plan as prep of their own, just as thawing does.

Questions
Can I prep two days ahead? Yes, if the rest allows it. Each rest has a minimum and maximum range, and the row will indicate if you planned outside that range. The focaccia's dough, for example, can rest from 12 to 72 hours, so its part 1 can be planned up to three days before it is baked.