Just to satisfy my curiousity, I just did a test. I created a drop-shadowed object in Draw 10 and exported it as an EPS. I then opened that EPS in Mac PhotoShop 5.5 (the newest I own) and created a new layer below the imported layer and drew on it. I got the dreaded white box.

However, I was able to achieve transparency by changing the upper layer (the one with the Corel image on it) to "Hard Light" mode. Objects below showed through as hoped with an applied tint in proportion to the darkness of a particular area of the feather-edged drop shadow, and were completely blocked by the box itself.

This is not really surprising, since the drop shadow has been essentially converted to a TIF and TIF's support transparency. The good news is that that conversion (within Draw) apparently effectively checks the "Transparency" box when it does so.

I hope this helps.