Is it possible to create a shortcut within a shortcut?
Not as far as I know. What’re you trying to achieve?
It actually is somewhat possible! You have to export a template shortcut to somewhere it can be downloaded from (amazingly iCloud links do not work as they are a link to a link to download). But there is a import url url for shortcuts https://support.apple.com/guide/shortcuts/import-a-shortcut-from-a-url-apd77a47304b/ios this was enough for my use case.
You can also embed a shortcut as base64 encoded text in a shortcut and then import it in Shortcuts.app with the Open In… action, pre selecting Shortcuts itself