Well all seems fine for local extension, you have placed them well under the extensions/@guptast folder.
Normally if you choose the extension folder when added the new extension it should be added also correctly in your project package.json, but seems it isn't
You can just remote if from the project options extensions list, save and then readd it again, not as new but as existing extension but with url: file:extensions/@guptast/wappler-csv-export-component
and on save it should be added and linked.
You can do it also manually but it is better to use the project options / extensions
to check in your project package.json if you are installing them locally you will see:
"@guptast/wappler-csv-export-component": "file:extensions/@guptast/wappler-csv-export-component"
when installed a virtual link folder will be created under node_modules (if it is a docker project then it will be under the node_modules in the docker container)
and then in the Project Assets updater, files to be copy will be shown.
do note that for docker indeed you will need also a copyFiles. as Brian indicated. in:
So it might be better to develop extensions with local node server.
But I will also make sure we generate this copyFiles.js scriptipt automaticlaly in the future.