Dropdown within a dropdown?

Hi brilliant excel wizards!

I have a sheet that contains the dropdown options for a budget. I used data validation on another sheet to create the dropdown. The problem is that there are a LOT of options.  Here is a partial of the choices within the dropdown:

As you can imagine, the list is quite long. It would be wonderful if somehow, they first select the main category and then the line-items for the selected category show as additional options. I am using office 365. I don't want to assume that excel isn't capable of doing this in one cell so I thought I would throw it out there to you all! Maybe it is possible?

If that doesn't work, I was going to try to solve the problem with using color but I don't see how to set up a dropdown to display the color (as you can do in GSheets) within the dropdown list. I see I can use conditional formatting once the selection is made but that doesn't really solve the usability issue.

Any ideas? 

Thanks!