Martin

@Patrick: Can you think about anything which does not allow to see the existing Enigmail icons if these compose_action icons of other plugins are present?

Thank you for your message. It looks like this addon (with the button cloud_johannes-endres_de-composeAction-toolbarbutton) really prevents the icons for showing up. I'll try to address the problem with the addon author. Thanks again!

I have the same problem using Thunderbird 68.10.0 And Enigmail 2.1.7. I digged a bit deeper and noticed that the buttons are there but just not visible. Here's something I found in xulstore.json which is the file where the toolbars are stored: "composeToolbar2":{"currentset":"button-send,separator,button-save,priority-button,button-attach,cloud_johannes-endres_de-composeAction-toolbarbutton,spellingButton,button-quicktext,button-enigmail-sign,button-enigmail-encrypt,button-security","mode":"full","iconsize":"large"}...