Hi Tom! You can use checkboxes in Smartsheet, however they are slightly different than in Trello. In Smartsheet, there is a Checkbox type column. You can add this column to your sheet in the Grid view by right-clicking any column header, then selecting Insert Column > Checkbox. You'll want to insert a new column for each item that would be in your list in Trello. Then, when you go into the Card View, you will see the checkboxes displayed.
Let me know if this doesn't accomplish what you're looking for and I'll pass your feedback along to our Product team!
