Thank you for explaining the CoverUrl behaviour. I will come back on this in a separate feature request posting.
I want to add, that I actually know two ways of transferring information from ParserScriptIndex to ParserScriptAlbum, but both are so clumsy that I didnt want to list them in the original post.
First, you can add your information add the end of the Album url. You can for example append a dummy parameter &mydata=somestring. Restricted access to this information is possible with SayOutput "CurrentUrl" from within the ParserScriptAlbum block. Did I call it clumsy?
The second way is similar, but uses the PreviewUrl. Add the %_preview% to the IndexFormat, provide the data in the album urls where indicated from the %_preview% pattern. Access is possible through SayOutput "CurrentPreview". Of course you'll loose the preview feature in turn, but you can at least get one block of data from the first to the second block. Additional benefit: you dont have to worry about entity encoding and similar stuff - you get the data provided as %_preview% back unmodified.
Regarding your " " trick. If my goal was to supress the old information that would be a way to go. But I want to delete the tag itsself so i suppose i need the additional remove action. I will adress this as well in feature request.