I am running SD for Android version 3.0.5.18699. According to the Flying with Skydemon video, some aerodrome charts are available as overlay on the map. In the video the example with the aerodrome EGKB is shown, so I downloaded the UK maps and the charts for EGKB. But there is no yellow aeroplane symbol on the chart list, which should indicate that overlay is supported. The documentation doesn't say that this feature is iPad specific. So why don't I see the yellow aeroplane symbol on the chart in the Plate tab?

Not having an universal PDF library available does not mean it's impossible to have. I know at least 2 other tools that have this capability on Android and it's been available for a long time for both of them (in a fast and reliable way), even if they are not as efficient on many other aspects.