Access value holder of code template which is included in template list

The only way would be to move the VH1 to your top level template and then pass it to the lower level template as an argument. So in Codetemplate1Level1 it would be a real value holder, and in the CodeTemp1 you would change its multiplicity to "Single Argument". Then in the Codetemplate1Level1 in the value holder that points to your template list provider you would need to add a dynamic argument override, call it "VH1" and point to the VH1 value holder. This way the provider would be able to pass its value to the underlying CodeTemp1 when it is selected.

Doing the other way around is not possible because when template other than CodeTemp1 is selected in the template list provider, the VH1 does not exist and the system cannot figure it out on its own. You can implement your own custom provider that would be able to retrieve the value using repository APIs (or substitute something when it is not defined), but as Jostein suggests, there should be an easier solution to what you are trying to do. Custom providers should be the last resort.