Finale has actually had this capability as long as I can recall, but I recognize that you're asking for this as a feature because of not knowing of the process. Finale has so many capabilities, it can take a while to discover how to accomplish a number of tasks, and even very experienced users may still discover new shortcuts and abilities, so I hope you'll find this feedback from the Finale manual useful:
Type the chord that you want to appear in the score, such as “BbM7/C”. Type an underscore (SHIFT+hyphen) instead of a slash (such as “BbM7_C”) if you want the alternate bass note (C in this example) placed UNDER the root. You can also use a bar(SHIFT+backslash, “BbM7|C”) to place the alternate bass note slightly to the lower right of the chord.
If you wish to change the appearance of chords which have already been entered, I recommend searching the manual for "Change Chord Assignments dialog box" in the manual - but basically: This dialog box lets you change all chord symbols in a selected region in several ways. You can transpose them, turn their playback on or off, change their display to fraction-style, or move them by a precise amount.
To be honest, Bob, I think the best process to find what you're looking for would be to search for 'Chords' in the Finale manual: which you can access from the Launch Window or the Help menu. There are so many different facets of chord input you might wish to control – from chord styles to metatools... and I found my information from the Finale manual also. Many different pages and options present themselves when you search the manual; whether there's a chart for what you might wish to do, I don't know– but I've found it useful to collect and print notes for myself on a variety of processes which I don't use everyday, but may still need to recall from time to time.