code/modules/minimap/hud/minimap_toolbar.dm

/atom/movable/screen/minimap_toolbar_button/erase	Erase tool — left-drag on the map to erase a line.
/atom/movable/screen/minimap_toolbar_button/clear	Clear tool — removes all drawings and labels.
/atom/movable/screen/minimap_toolbar_button/label	Label tool — click the map to place labels, right-click a label to remove it, right-click this button to clear all labels.