I've been trying to edit the default .Net core templates installed with vs2019 but I can not find where they are stored I checked:
.\Microsoft Visual Studio\2019\Community\Common7\IDE\ProjectTemplates\CSharp\
but that directory only contains .Net Framework project templates.
You didn't include the entire directory address of where you checked, so I'll assume you haven't looked in the following locations from the docs. Check these directories, they should contain all the templates installed. I just checked mine, all there.
%ProgramFiles(x86)%\Microsoft Visual Studio\2019\<edition>\Common7\IDE\ProjectTemplates\<Language>\<Locale ID>
%ProgramFiles(x86)%\Microsoft Visual Studio\2019\<edition>\Common7\IDE\ItemTemplates\<Language>\<Locale ID>
NOTE: These are default installation locations! If you installed to a custom path, different drive or if you changed the template location yourself, then obviously they won't be there. If you still can't find them, go into VS and check Tools > Options > Projects and Solutions > Locations and see what it's set to.