OVERVIEW
NBP Plugins feature the ability to hide the panels when not being used. This can be disabled in the settings of the plugins.
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NBP Plugins
Why Doesn't My NBP Plugins Show In Photoshop?
Verify the plugin is installed correctly. Under the Filter menu in Photoshop, verify that NBP can be seen at the bottom of the filter menu. If help is needed in verifying the installation, refer here: A NBP Plugin Doesn't Work, What Should I Do?
The Plugin Panel Closes Automatically Whenever I Click On It, Why?
To automatically show or hide iconic panels when working in Photoshop, press Ctrl-K (Mac: Command K) to open the Preferences. Check the Auto-Collapse Iconic Panels checkbox in the Workspace tab to enable or disable it (or right-click on the panel tab and select this option) depending on preference. This option makes it so that panels will automatically collapse back into an icon when clicking anywhere outside of the panel.