As you may know, the best practice/recommendation when deploying resources in Azure is to use an automated solution, such as DevOps.
That said, there is always situation when you need to deploy the resource using the Azure portal.
Well, good news as now you can set the size of the OS drive when deploying new virtual machine instead of using the default image size.
You can not fully set the size; you have to choose from pre-defined different sizes which vary from the image selected when creating the virtual machine
This option is quite useful if you need to reduce the size for cost optimization or have a bigger OS size.