Sub brackets not for all instruments

One publisher only wants a sub-bracket after the trumpets, horns and trombones have been merged. Dorico only makes a sub bracket for all or nothing. Is there a solution with 30 movements in the project a lot of work to correct this problem piece by piece?

There are a variety of options in Layout Options. Are none of them what you want?

Unfortunately, the various options do not help in my case!

You’ll have to use a bracket and barline change at the start of each flow.