On Windows
Go to Start > Settings > Apps and choose Ceacle Mockup and Uninstall.
For Photoshop 2021+, if the panel was not removed, go to Adobe Creative Cloud Desktop > Stock & Marketplace > Plugins > Manage plugins and Uninstall Ceacle Mockup.
For Photoshop 2021+, if the panel was not removed and you don't have Adobe Creative Cloud Desktop, use Anastasiy to remove the panel. Get Anastasiy.
On MacOs
Go to Applications remove Ceacle Mockup.app. Go to Library/LaunchAgents and remove com.ceacle.mockup.render.plist Go to Applications/Adobe Photoshop YEAR/Plug-ins and remove ceacle_mockup_plugin
For Photoshop 2021+, if the panel was not removed, go to Adobe Creative Cloud Desktop > Stock & Marketplace > Plugins > Manage plugins and Uninstall Ceacle Mockup.
For Photoshop 2021+, if the panel was not removed and you don't have Adobe Creative Cloud Desktop, use Anastasiy to remove the panel. Get Anastasiy.