e·li·sion
Elision is defined as the omission of a vowel, consonant, or syllable while pronouncing or writing something, sometimes as a natural shortening, as in “he’s,” sometimes for literary or poetic effect, as in “’tis”.
In vocal music, elision slurs are the curvy ligatures used to connect two lyric syllables under one note. This type of markup is quite common in vocal music in a language other than English:

In Finale, the process to show two elided syllables on the same note should be very straightforward. One could ideally type a specific keystroke to produce the elision (it’s a underscore in Sibelius) and you could type these in on the fly.
In Finale, you use a single keystroke to create the elision character; SHIFT-I. But even in Finale 2012, the process described in the User Manual requires several steps:
more >> “Creating lyric elision slurs more easily in Finale 2012 and earlier”