To add input objects to an existing boolean node
By default, clicking the button in the Poly Modeling shelf or the Modeling Toolkit performs a Difference (A-B) operation. You can also right-click the buttons and select another boolean operation to perform.
The additional input objects are added to the existing boolean node.
To add input objects to an existing boolean node using the Boolean stack
Your selection is applied to all new inputs. By default, new input objects are automatically assigned the Union boolean operation.
To add input objects to an existing boolean node using the Outliner
Your selection is applied to all new inputs. By default, new input objects are automatically assigned the Union boolean operation.