Updated Version 1.7.5 ! 
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Now you can hold Shift key and click to select multiple shapes !
Just hold Shift key when you select shapes, it will add selected shape to selection! -
Now you can press H key to view full key reference on screen !
Press H key (works in both normal mode or selection mode)
You can mouse-scroll up and down to read, or you can press Arrow Up/Down key !
Enjoy !