A basic and properly structured HTML/CSS drop down menu can serve you just as well. In fact, it may make your site appear more responsive to not use animations and instantly display the menu instead.

CSS, or Cascading Style Sheets, defines the look and formatting of that HTML. Both are essential to coding your own website, and here's how to get acquainted with them.

So this is how you can enable multiple selections in a drop-down in Google Sheets. While this is not available as an in-built feature, you can easily do this with some Google Apps Script magic.