@MS Techie - Thanks for reaching out.
As @Limitless Technology rightly said about the fresh publication from Microsoft.
To your point, There is no New-AzSubscription command that I'm aware of, the New-AzSubscriptionAlias command is in preview.
If you want to use PowerShell, youneed to use the New-AzSubscriptionAlias
command.
See this article for more information: programmatically-create-subscription
Hope this helps.
If it does, Please feel free to "accept the answer" so it can be beneficial to the community.