Q:

Setting layer transparency in QGIS 3?

I just switched from QGIS 2.18 to version 3.0.3. In the earlier version, setting layer transparency was easily done with the "transparency" slider from the Layer properties->style tab. See image below:
 
The newer QGIS version, however, does not appear to display such a transparency bar, as seen in next image. Is there a simple way to change a layer transparency in this verion of QGIS?

A:

You have to click on the layer rendering arrow (see the bottom of your second image) to access the slider and other option.
in QGIS 2 it was on by default, in QGIS 3 it's off by default...

A:

As an alternative option, you can open Legend tab and select Opacity slider widget.
It will add an opacity slider in the Layers panel. 

