On the 4th bar first beat for the remaining 3 beats, until the next bar, enter g... for everything to sustain (this is called a hold)
With all of the tracks sustaining to your satisfaction, freeze all the tracks. Remove the freeze from the piano soloist and regenerate the track but before you regenerate the Soloist Piano, change the chord in the 4th bar to play a G rather than G... . The frozen sustained instruments won't regenerate ignoring the regeneration and play the sustain. The result should be all tracks sustained with the Solo track playing.

BIAB 2025:RB 2025, Latest builds: Dell Optiplex 7040 Desktop; Windows-10-64 bit, Intel Core i7-6700 3.4GHz CPU and 16 GB Ram Memory.