>Clicking eyedropper on area to get color, also performs actual click, losing selectionClick the "lock" icon in your inspector window and the selection will not be lost.
>Using middle-click to pan, if a GUI item is selected, when the middle-click is released it counts as a left click and selection is lostI can't reproduce this one. Middle mouse button never causes a left click.
>Holding "CTRL" or "SHIFT" to select multiple items often does not work, unless zoomed in fairly close, the click only selects the object and does not add to selectionThis is Unity. You need to double-click UIRoot to reset your scene camera's near/far clip planes, thus fixing the selection.
>With multiple objects selected (simple sprites, in my case), "Right-Click > Attach" menu is relative only to last-selected objectThis one I can fix.