life cycle

Extensions have two types of lifecycles depending on the target of the extension:

Application Lifecycle

Effective from the time Next Design is started until it is terminated (extension common to Next Design regardless of project)
Project life cycle

Effective from the time the corresponding project is created or opened until it is closed (extension for a specific project)

Extension execution flow

The general flow from loading the extension to executing the process is as follows.

When you launch Next Design, it loads the manifests and scripts and DLLs of all extensions located in the given folder.
The application lifecycle extension is enabled and adds the ribbon tabs and buttons defined in its manifest.
When you open a project with a project lifecycle extension target profile in Next Design, the extension is enabled and adds the ribbon tabs and buttons defined in its manifest.
According to the extension points defined in the manifest, command handlers or event handlers implemented in the extension are called when corresponding UI operations or events occur.

Please refer to Extension Deployment for the extension destination folder.
Even if you replace the extension or change the script while Next Design is running, those changes will not be reflected.
All extensions (manifest and DLL) are loaded when Next Design is launched and are not reloaded while Next Design is running.
Extension scripts are also loaded at the time of the first process call and will not be reloaded while Next Design is running.