Time Signature like America

If I understand you correctly, the time signature at the beginning should display as 6/8 + 3/4, right?

1) Time Signature Tool.

Select All, and set the time signature to 6/8 (work smarter, and use the context menu).

2) (Time Signature Tool)

Double-click the first measure.

In the dialog box Time Signature, expand the dialog box by clicking “More Options”.

Select “Use a Different Time Signature for Display”.

Set the “Display Time Signature” to 6/8 + 3/4 (Use the button “Composite…”).

3) Double-click the second measure.

Change the “Real Time Signature” to 3/4, but keep the “Display Time Signature” as 6/8 + 3/4.

4) Select the first two measures (NB: Stack Selection!), and Copy/Paste them as many times as needed.