Hello oliver42,
Thank you for using Apple Support Communities. It sounds like you want to know if there's a Siri command that will add new reminders to the top of your list. If so, we'd like to help answer your question. We also notice that you're already coming from the following resource here: Use Reminders on your iPhone, iPad, or iPod touch - Apple Support
This resource does dive a few examples on how to use Siri with Reminders:
You can ask Siri to schedule a reminder for you on your iOS device or your Apple Watch.* Here are a few examples:
* "Remind me to feed the dog every day at 7:30 a.m."
* "Remind me when I get home to check the mail."
* "Remind me when I leave here to stop by the grocery store."
* "Remind me tomorrow at 3:00 p.m. to call Tara."
When creating a new reminder manually or when using Siri, they will be added to the bottom of the existing list. Asking Siri to add the reminder "To the top of the list" will not work. If you go to Settings > Reminders on your iPhone, you will see there is no sorting option available. This is why Siri only adds new items to the bottom of the list. You can however, manually move the added reminder to the top of the list by dragging it with your finger.
If you'd like to provide feedback on your experience with Apple products or services, you can do so using this link: Legal - Unsolicited Idea Submission Policy - Apple
Thank you for using Apple Support Communities. Take care.