How to call out checkbox style when using the plugin called Things

What I’m trying to do

I installed a plugin called ‘Things’ under version ‘2.1.20’ and I want to use the checkbox style.
I want to know how can I callout that checkbox style by tying instead of copy the markdowns
to get the visual effect.

Things I have tried

Taking - [?] question as an example
type : - [?] but the ‘-’ made '- [?] ’ a bullet point