Replace plugin with non-packagist composer version, in custom location.

composer.json

{
  "repositories": [
    {
      "type": "vcs",
      "url": "https://github.com/wp-shortcake/shortcake"
    },
  ],
  "require": {
    "oomphinc/composer-installers-extender": "^1.1",
    "fusioneng/shortcake": "dev-master#0.7.4"
  },
  "extra": {
        "installer-types" : [
            "library",
            "phpcodesniffer-standard",
            "project"
        ],
        "installer-paths": {
            "plugins/shortcode-ui": [
                "fusioneng/shortcake"
            ],
            "plugins/{$name}": [
                "type:wordpress-plugin"
            ]
        }
    }
}

gistfile2.txt

The extras > installer-paths > plugins/shortcode-ui key is only required for custom installation (by default this installs insto plugins/shortcake.

This plugin  is not available from packagist thus a VCS repository tag is tracked. 

terminal.sh

git rm plugins/shortcode-ui -rf 
composer update fusionend/shortcode