The Model Only tools are only used in ModelBuilder. Some of the tools are used to control the flow of processing while others are simple support utilities. Learn more about using Model Only tools in models.
ArcGIS Model Tool2: Using Model Only Tools in ArcGIS Model Builder
1.3.2 Opening and exploring ModelBuilder GEOG 485: GIS Programming and Software Development
Tutorial: Executing tools in ModelBuilder—ArcMap
Model Only Tools Collect Values
Getting Started with Model Builder
Solved: Is there “export to graphics” tool in the model bu - Page 2 - Esri Community
Examples of using Model Only tools in ModelBuilder—ArcMap
ModelBuilder App Adds Fields in Bulk to Datasets
Tutorial: Creating tools with ModelBuilder—ArcMap