The widget templates and everything else in the Sitefinity Explorer are using the active Sitefinity connection.
In contrast, the Solution Explorer is using the file system to edit a local project. There are several features like the Dynamic Items Field Control Selector that are using the connection to help you create the required items, but for those you need an active connection to the site you have currently opened anyway.
Thunder is editing the local ToolboxesConfig.config because this is where you have created your widget. If we register it in the remote machine's configuration as well, it will work only after you copy the files and build the project.
We will take your feedback into consideration. Please let me know if I can be of further assistance.
All the best,
the Telerik team
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