I decided to delete this post …
There are limits to the number of items that will show in a data validation drop down list:
- The list can show up to show 32,767 items from a list on the worksheet.
- If you type the items into the data validation dialog box (a delimited list), the limit is 256 characters, including the separators.
The approach, in my deleted post, used a delimited list. It was, therefore, limited to only 256 characters. For me, for anyone, not worth the trouble.
I first programmed this in 2014, I observed the limitation then but had since forgot about it.