The symbology windows allow you to manage the style of each layers. You have several options available depending of the layer's style.

1. Points style managment: you can change the color and the radius of the points
2. Transparency management
3. Apply or cancel the modifications

1. lines style management, you can change the color the width and the shape of the lines. There are few choices of shape
   
2. Transparency management
3. Apply or cancel the modifications

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1. Polygons style management: you can change the border width and color as the fill color and style. There are few Styles available
2. Transparency management
3. Apply or cancel the modifications