Hi, I just wanted to quickly ask why in order to get a trill line I must first toggle the tick box on that allows me to get the trill line once I check it. Isn’t just the toggle enough for this task, or is there a situation where having the tick box toggled on but unchecked brings some workflow advantage I’m unaware of? Thanks!

The toggle indicates that you’re overriding the setting in Engraving Options; the checkbox indicates whether you want a line or not.
So if you have the global option set to always show:
And there’s a particular trill where you don’t want a line, you would toggle the property override on but leave the box unticked. Without both controls, there would be no way to indicate this.
In your case, I’m guessing you have the global property set to either tied notes or do not show, and you have a trill where you do want a line. So you toggle on the override, and then you tick the box to indicate that you want a line.