you stil can read, but not store files everywhere anymore
try the following steps
- export your project and store it in a save place as backup
- copy the downloaded aia file and open it using 7zip
- go to the folder assets/external_comps
- to manually import an extension, open the aix file using 7zip, you now have two 7zip windows open in parallel
- drag the main folder of the extension from the aix window into directory external_comps of the project and overwrite the existing old directory of the extension
- upload the modified project into App Inventor
Taifun
Trying to push the limits! Snippets, Tutorials and Extensions from Pura Vida Apps by 
Taifun.