Selecting All Objects in a History Tree Folder
The history tree organizes objects in several categories. Right-click on the group for solids, sheets, lines, non-model objects, or unclassified objects to see a shortcut menu command that lets you Select All members of that category.
Under each folder, you can also Select All for objects of the same the material or parts of the same assignment at once. When you right-click on a solid folder, the menu lets you check whether to organize objects by assignment. For example, this history tree has Solids organized by object:

This history tree has Organize Objects by Material selected:

This history tree organizes Sheet objects by object:

This history tree has Organize Sheets by Assignment selected:

Selected objects are highlighted in the modeler window view area.
Related Topics
Selecting All Faces of an Object
Setting the Default Color and Transparency of Selected Objects