The online version of Excel does this and will be coming to the desktop Excel 365 version 'soon'. You can presently have your drop down list filtered by text you type into the cell but the way that works is that you type some characters into the cell and THEN you click the drop down button and see a filtered list of options (i.e. it is not dynamically happening as you type). If you want help/instructions on how to do that here is a good link: https://www.xelplus.com/searchable-drop-down-list/