I haven't needed to do this for over a year, but I just tried in 2018.4 and the functionality is not there any more 😞
I'm trying to open an Excel file and customise the SQL used to read the data.
I've found this in other posts:
https://community.alteryx.com/t5/Alteryx-Designer-Discussions/How-do-I-get-row-range-in-Excel-format...
then I found this one 😞
https://community.alteryx.com/t5/Alteryx-Designer-Ideas/Input-Tool-2018-1-Excel-Range-Feature-Remove...
Hopefully this feature will be re-instated soon 🙂