Duplicate entries do not merge on import

I often turn glossaries into Termbases, but the problem I always run into is that may glossaries have multiple terms in the same entry. For example (my languages are English and Portuguese): English term: dog - Portuguese terms: cachorro, cão. If I simply import the entry that way, when "dog" appears in the source segment, the translation will appear as "cachorro, cão" in the Term Recognition window. So what I do is I add another line in the Excel sheet I'm going to import into the termbase so that I have one line with "dog - cachorro" and another line with "dog - cão", which creates two entries. What I want, in that case, is that the two entries are merged on import so that "dog" will show up in the Term Recongition window, followed by two entries in Portuguese:

cachorro

cão

I have tried choosing the import definition "Synchronize on Term" which is described as "Add entries as new entries. However, if entries with the same term exist already, then the entries are merged." But after the import, the only entry is just "dog - cachorro" and the second line, "dog - cão" is cimply eliminated and the two Portuguese terms are not merged into one entry for "dog".