"On my Google Earth there is a toolbar at the top of the screen. One of the
tools is something called "Add Placemark" which has an icon which looks like
a thumbtack. That is the tool which allows you to simply click on the screen
to add a location. It allows you to change the icon from the thumbtack to
another. (I changed mine to a square target instead of the thumbtack.)
"In addition, after you add the placemark, you can then just move it around
at will, which makes it easy to reposition and get new coordinates. The
placemark has an "info" screen that has the coordinates that you can copy
and paste from."
Using GPS Visualizer, below, it has been possible to load the entire database into Google Earth.