I know this seems a little simple but I was just having the same difficulty as you – I had installed the plugin and yet there was no button showing in the editor.
However I’ve realised that the editor integration seems to be turned off by default. So when I went into the GDE Settings and clicked the Advanced Options at the bottom. In the list of options that appeared I unclicked the top one, called Disable Editor Integration.
Once I did that everything seemed to work okay…
