I don't know how Print Music does it. It might be similar to Finale.

In Finale, you

click on the chord tool/chord menu-choose type into score/type a capital letter (ABCDEFG)

to add a sharp press shift 3    to add a flat-lower case b

then, type a colon : and 0 "zero" then push enter. This will show you all the suffixes you have available. Double click on a suffix.

Notice the numbers in the upper left hand corner of each chord. If you can memorize these you can speed things up considerably. Just enter the chord root (with a flat or sharp if needed) and then type a colon & the suffix number of the chord you want.

For example C#:6 would be a C#min7 chord (#6 is a minor 7th chord in my chord list) Remember, you can always type a 0 (zero) after your colon if you need to see a list of all your chords.

I have sent in several emails asking Makemusic to let us leave the chord window open until we close it. That way your chords and corresponding suffix numbers will be on screen at all times so you won't have to memorize them.

There are other ways to enter chords but I think this is the best way.