FileMaker - Dropdown menu with checkboxes and multiple choices

No, a DropDown list or Popup menu that allows multiple selections by clicking next to each menu item is not an option in FileMaker, nor is it using the Troi Dialog plugin with which I'm also familiar.

However, a good option in this circumstance is to use a "Popover" window that contains the values in Checkbox form. This allows the user to make multiple selections without taking up the as much room on the main layout. If you wish you can display the selections on the main screen as a text string using a calculation field and then putting it on the layout as a Merge field  <<SelectedOptionsString>>

Note that when a user selects multiple options from a checkbox value list, the options appear in the list in alphabetical order, but the selections are entered into the field a carriage-return separated values in the order that they were selected. (Which has many interesting uses). For example, if the checkbox value list contains:

Apple
Banana
Blueberry
Orange
Pear
Peach

and the user selects Pear, Apple and Peach in that order, if you look at the contents of the field without the checkbox value list formatting you will see a list in the order it was selected:

Pear
Apple
Peach

There are ways to sort the values after selection if that is important. I normally use a Custom Function to accomplish this.

Thanks
Would you be ok to attach a small example so that I can see how it looks like and how it works?

Great solution! Thanks!