For what you want to do, can you not use the composite time signature tool to create the actual time signature? Then all you'd have to create are the largish parenthesis (which you might be able to do with fonts and the text tool).
You could put the 10/4 in an otherwise blank measure with no bar line. Shrink the measure until it just fits the 10/4 nicely, then put the 3/4 + 3/4 + 4/4 with parenthesis around it in the first real measure.
There are advantages to making it all one single graphic, but
I thought this might be easier.
Finale 2004b, XP Pro // P4, 2.6 GHz, 2 Gb RAM, SB Audigy
First commission: March, 2004; First Concert: June 6, 2004