To do this...
Select a part on a model | Do this on the assembly tree...
Left-click | Do this in the viewport...
Right-Click |
Select multiple parts on a model | SHIFT+Left-click | CTRL+Right-Click or SHIFT+Right-click+Drag red selection box to encompass parts |
To add parts to a selection | | CTRL+SHIFT+Right-Click+Drag red selection box to encompass parts |
Deselect all parts | Right-click on background | |
Deselect all except chosen part | Right-click on chosen part | |