VERIFIED SOLUTION i

Toggling Legend Grid Lines using MapInfo Pro and MapBasic

Product Affected: MapInfo Pro 64-bit
Product Feature: Legend Designer
In MapInfo Pro 64-bit versions, Grid Lines in the Legend Designer window can be toggled via ribbon interface:

User-added image

The below MapBasic command can also be used within MapInfo Pro or in MapBasic application to toggle the Legend Grid Lines:
Run menu command 2809

 
UPDATED:  July 16, 2019