Q. How can I create a multiselect dropdown list in an Excel worksheet?
A. Data Validation works great with single selections. To allow for a multiple selection field, you need to turn on your Developer tab and insert a form field.
First, I recommend typing your selections in a different work sheet and naming the range. Then insert a List box control. To make it usable, you need to stretch it tall enough to accommodate all your selections. Then, with your list box selected, click Properties, and type your range name in Input Range. Be sure to click the Multi radio button before clicking OK.
You could also use multiple check box form controls. The latter is recommended if you want to export the answer data for analysis. In this case, you need to name a range, because each checkbox control would have its own text label.