I found a bug with a plugin that I was able to correct, but I an unable to reach the author of the plugin, nor can I create an issue with it.
https://www.dokuwiki.org/plugin:codebuttonmod1
https://github.com/user9209/dokuwiki_plugin_codebutton
Issue:
The icon does not display in the toolbar properly, yet a space is there and is clickable.
Remedy:
edit action.php
.../lib/plugins/codebuttonmod1/action.php
Replace:
line 28 'icon' => '../../plugins/codebuttongs/image/code.png',
with:
'icon' => '../../plugins/codebuttonmod1/image/code.png',
Code Button will now appear.