Or if you’re instead in the mode of deciding what to do next, or making a schedule for your day, etc., then that’s different, but working memory is still kinda irrelevant because presumably you have your to-do list open on your computer, right in front of your eyes, while you do that, right?
Whenever I look at a to-do list, I’ve personally found it noticeably harder to decide which of e.g. 15 tasks to do, than which of <10 tasks to do. And this applies to lists of all kinds. A related difficulty spike appears once a list no longer fits on a single screen and requires scrolling.
On this topic you might be interested in skimming Zvi’s three dating roundup posts. Here’s the third, which covers dating apps in the first two headings, but all three posts mention them a lot (Ctrl + F “dating app”).