I just heard from Corel Customer Support. Their response is, "I am sorry to inform you that Easy CD & DVD Burning does not support 'My Disk Gallery' files, nor does it have an equivalent feature. None of our current Roxio products support, or have, this feature."
Fortunately I've found some open source shareware that looks it will enable me to continue burning and cataloging DVDs, however there doesn't appear to be anything yet that will read my old Roxio database. Regarding that legacy database, the good news is that I have installed Roxio Easy Media Creator 10 on an old Vista machine and it appears to be working fine.
My apologies to the moderators if I came across as confrontational. Easy Media Creator 10 Suite has been my reliable DVD burning and cataloging solution for years, and to suddenly discover that my catalog of 600+ data DVDs (I'm a computer graphics illustrator with many projects to archive) had become obsolete--and inaccessible--was a bit of a shock.