About "text snippet" I already know how to use it, maybe because of the language difference, your language is English, so the trigger mode is: add space after the date to work.
However, you have ignored the other language countries, such as China 
, when the time of the field in the middle of the text, the function will not work, and even if the time to the beginning, add a space is not in line with our habits, it will be very strange, due to cultural differences, I do not know so that you can understand?
The idea of "text snippet" is really like the operation in "Quick Action", a very clever design, but is it not necessary to recognise the time in this way at the moment? Because Apple's official reminders are able to recognise the time automatically (but can't be set automatically). But the following app has already done it, I hope you can refer to it, and I hope very much that you can launch this (I can't send the video here, I've already sent it to you via email)
For multiple choice tasks, I have also recorded a video for you, hope it can help your development work. (Can't send the video here, it's been emailed to you)
For the incomplete widget list, I tried your method but it didn't work, and then I found the same thing on iPad, is it possible that the "next" widget can only be dragged to the "today" list? If so, I would like to open up all the lists so that my iphone interface can be fully populated with your widgets, but at the moment it's not enough for this reason.
