I use the “Don’t Merge” mode. I was surprised to find that, for example, if I see “la hermosa ciudad,” and first click “hermosa,” then click “ciudad,” and finally click-drag “hermosa ciudad” to check whether this is some sort of set phrase, it causes the word entries for “hermosa” and “ciudad” to be deleted. That behavior doesn’t make sense to me, at least because I might be wrong in guessing that it’s a set phrase. But even if I was right, I don’t see why I wouldn’t still want glosses for the two separate words.
Is it perhaps a bug?
Also, using auto-highlight modes, if I ensure that word entries exist for “hermosa” and “ciudad,” as well as for the combined “hermosa ciudad” entry, then across different texts that both contain the term “la hermosa ciudad,” I see a lot of inconsistency in whether the combined phrase “hermosa ciudad,” or the single word I happened to click, are offered by the context dialog box. I am not sure what governs this. In general it seems that I can force a change in what is displayed by switching back or forth between auto-highlight of “All Your Words” vs “Ready To Learn” words. (Note that all three word entries were created at about the same time and were never practiced or recalled.)