So, I know that for Dorico 2, if you want to create a pick up bar, you should show the pop over and then input, for example 4/4, 1. However, I do not know how to make the last measure have only 3 beats in that case. How do I do it?
Several ways. You can make the last measure 3/4 and hide the time signature. That’s probably the most straightforward, and will preserve note spacing.
How do I hide the time signature?
Click on it to select it, Properties panel (Ctrl-8), and it’s an option.
You don’t need do anything with time signatures. Enter the notes, then insert a final barline at the right place in the last bar.
If that leaves you with an empty bar after the final barline (which it probably won’t!) just delete the unwanted bar.
Even better, thanks Rob. Still working to shed my Finale way of thinking about meter…
I simply start typing and when I want the first bar line use the bar pop over and type |. When I get to the last bar use the pop over and type 
(if you want a repeat). The empty bar, or bit of a bar, that is left can be dealt with by going to Trim Flow. It works for me and I have to say is easier and more intuitive than some other music engraving programmes I could mention…
ha! I see that the auto emoji has created a face… I meant type: followed by |
How do I do that insert final bar thing? Will it automatically accommodate the pick up bar?
Put the caret where you want the final bar. Invoke shift-b, write fin
Invoke shift-b again and write trim (to get rid of extra beats after the final bar.