*** Sorry Sven for sending twice, but I forgot to send to gimp-dev list. ***
Hi Sven. You always help me!
> Sorry, but you can't. Currently the procedure that opens the thumbnail
> can only specify the size of the original image. We could add the
> possibility to optionally the specify number of layers. Currently it is
> not possible though.
If I can write a patch, I will send it to bugzilla...
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