When I export a shapefile to Excel from ArcGIS using ModelBuilder the header maximum length is 10. I would like to know how can I have more.
I don't think it's possible. This is because shapefiles cannot store field names of more than 10 characters. (Shapefile is an old format from the 1990s)
If you convert a data table into shapefile format, the field names are truncated (if longer than the limit). So, if you had longer field names, the information is already lost when it's converted to a shapefile.