Hi skuddledudd (superfun to say btw :),
Since I revised the nesting logic, it was hard to be precise about converting old libraries. It used to seek common categories and automatically make them the top nest, but now it's just arbitrary (you may try Ctrl + dragging objects or Move/Insert functions btw). So a little housekeeping might be in order after the conversion, or you could arrange the Excel file so that it would import perfectly (the ParentID of the children needs to match with their parents ID).
In settings, you may set the "default" colors/fonts etc. and the new objects will be generated with these settings. However, currently it is not possible to change the settings for objects in bulk. In selection mode there's a few collective change options, I'll add this function there, it shouldn't be too hard.
Thank you for the quick (and encouraging) feedback!