Note: this is an experimental feature, subject to change or withdrawal.
From v10.0.0, in the text pane, Edit ▸ Insert ▸ Checkbox adds a checkbox to the text. Clicking on the checkbox checks and unchecks it. The list attribute $TextCheckboxes reflects the state of each checkbox in a note; the nth element is true if the checkbox is checked, and false otherwise.
For the present, expressions and checkboxes embedded in the text are ignored on export.
See also—notes linking to here: