These are a set of multi tools (only one at a time is shown on the
toolbar). When the current tool is clicked and held with the left
mouse button then a drop down box with the other tools appears.
Selecting any of these with the left mouse button makes it the current
tool.
To make the drop down box appear more quickly click right on the multi tool.
The + magnifier (zoom in) and - magnifier (zoom out) are
actioned immediately.
The broken box magnifier (zoom in area) - requires that an area be
dragged out
using the select tool in the schematic. The schematic is then
zoomed in to this area (limited to the allowed zoom
magnifications).
Zoom center makes the middle of the schematic appear on the screen.