I've got a great problem with the smart objects in my project:
I imported some Images (no background) which had the file format 'png'. I just dragged and dropped the files into my current photoshop window. They got imported and then automtically converted into smart objects.
After that I created a lot of copies of these smart object and transformed them.
Now I wanted to change one of the smart objects and double clicked on it. But unfortunately the opened file is a png. So it's not possible to save layers in this smart obejct
Is there any way to change the file format of a smart obejct (like psb/psd)?
Yes. Open an SO into a doc window/tab, edit it or whatever, do a Save As to PSD (or any other format). It'll be saved into a temporary folder. Close the SO doc window/tab. In the main doc window/tab, right-click the SO's name in Layers panel, pick Replace Contents and select the file you saved in the temporay folder. All instances of the SO will be auto-updated.