The drop down feature does not include the option to select more than one item. Here are some articles that discuss some workarounds
Select Multiple ItemsOctober 15, 2018
https://www.contextures.com/excel-data-validation-multiple.html
Instead of limiting a data validation drop down list to a single selection, you can use this macro to allow multiple selections. Video and written instructions, and get the free workbook to see how it works.
**Selecting Multiple Items in Data Validation List******March 3, 2016
http://www.myonlinetraininghub.com/selecting-multiple-items-in-data-validation-list
If you want to limit the choices available for the values that can be entered into a cell, you could use a data validation list. In the example image below, we are creating a roster for the teachers that are on playground duty during the week. The data is laid out as a table, and […]
**Data Validation Multiple Selection Edit** – Drop Down List Multiple Select October 22, 2015
http://blog.contextures.com/archives/2015/10/22/data-validation-multiple-selection-edit/
If you select an item from a data validation drop down list, it’s entered in the cell, replacing any existing data in the cell. If you’d like to add more items to the cell,...
**Select Multiple Items From Long List in Excel******December 11, 2014
http://blog.contextures.com/archives/2014/12/11/select-multiple-items-from-long-list-in-excel/
It’s hard enough to select one item from a long drop down list – how can we make it easier to select multiple items for a cell? In the screen shot below, the worksheet...
**Multiple Selection Drop Down With Codes******January 21, 2014
http://blog.contextures.com/archives/2014/01/21/multiple-selection-drop-down-with-codes/
There is a sample file on my website that has VBA code for selecting multiple items from a data validation drop down list. You can insert all the selected items into the active cell,...
**Drop Down Multiple Select or Remove******September 9, 2011
http://blog.contextures.com/archives/2011/09/09/excel-drop-down-multiple-select-or-remove/
There’s a popular sample file on my website, that lets you select multiple items from a data validation drop down list. Since the original article, I’ve posted updates: how to set up multiple selection...
**No Duplicates in Multiple Selection Excel Drop Down******July 25, 2011
http://blog.contextures.com/archives/2011/07/25/no-duplicates-in-multiple-selection-excel-drop-down/
Thanks to an email question from Leslie, I’ve done another variation on the Data Validation Multiple Selection sample. Leslie is scheduling training courses, and has a table with dates across the top, and course...
**Drop Down Multi-Select Update******July 8, 2011
http://blog.contextures.com/archives/2011/07/08/excel-drop-down-multi-select-update/
I’ve done another update to the Data Validation Multiple Selection sample, thanks to a question from Pat, in a blog comment. He has 3 columns with different drop down lists, and wants to add...
**Set up Multiple Selection Excel Drop Down******April 29, 2011
http://blog.contextures.com/archives/2011/04/29/how-to-set-up-multiple-selection-excel-drop-down/
[Latest update: July 27, 2016] With a bit of VBA programming, you can change an Data Validation drop down list, so it allows multiple selections. There is a sample file and instructions,...
**Edit Multiple Selections in Excel Drop Down******February 28, 2011
http://blog.contextures.com/archives/2011/02/28/edit-multiple-selections-in-excel-drop-down-lists/
A couple of years ago, I described how you could select multiple items from an Excel drop down list. One of my clients needed that feature in a workbook last week, so I’ve made...
**Select Multiple Items from Data Validation List******September 18, 2009 http://blog.contextures.com/archives/2009/09/18/select-multiple-items-from-excel-data-validation-list/
You’ve probably used an Data Validation drop down list, where you can click the arrow, and select an item to fill the cell. In the worksheet shown below, you can select a month...