The many, many options in the “Manage Reminders” popup when creating an event are a pain. They can be difficult to scroll through, especially on a computer (as opposed to a touchscreen). I mean, does anyone really need to set reminders for exactly 21 hours before an event? Even if they do, having a text box and an “hours/days” popup would better fit those unusual cases.
Here’s what the analogous option in my calendar program looks like. Scoutbook’s should look similar (though not identical).