There are 3 ways to select multiple elements on Infurnia, as show below:
Selecting one by one:
Press either the Shift or Ctrl key, hold the key, and simultaneously click on the elements one by one via mouse/trackpad.
Blue-window selection:
Using mouse/trackpad, click on top left of the elements, hold and drag diagonally to bottom right. A blue selection window will form. Release the mouse/trackpad, and any object covered entirely by the window will be selected.
Green-window selection:
Using mouse/trackpad, click on top right of the elements, hold and drag diagonally to bottom left. A green selection window will form. Release the mouse/trackpad, and any object covered entirely OR partially by the window will be selected.
To deselect a selected element, press either the Shift or Ctrl key, hold the key, and simultaneously click on the selected element via mouse/trackpad.