Charlotte Poletti,

Before we can help you, we need to understand better.

1) Are you an experienced Finale user?

2) Are you talking “Finale-speak”?

… if a repeat ending is at the right end of a system …

3) Do you mean a Repeat Ending, or a Backward Repeat Bar ?

… I would like to have one long barline connecting all staves of that system …

4) Do you mean Barline connecting, or do you mean Repeat Bar connecting?

Peter, how did you make that bottom example? The Repeat Bar connecting?

… Peter, how did you make that bottom example? The Repeat Bar connecting? …

In this case (Charlotte Poletti) the problem is, how to break the Repeat Bars everywhere, except for some (few) cases where the Backward Repeat Bar ends a system.

The first part of the trick is two staff groups that both include all the staves, one group with Invisible Barlines:

The second part of the trick uses the Staff Attributes, via the option {Break Repeat Barlines Between Staves}.

(This step is not necessary for the Top Staff):

Where the Backward Repeat Bar should connect the staves (= at the end of a system), a custom staff style is used to de-select {Break Repeat Barlines Between Staves} in that very end-of-system measure only: