Which notes to hold
Sometimes a chord genuinely can't be held whole — the hand runs out of fingers, or the tempo doesn't leave time to set every finger before the bow needs to move. This is the professional's triage, not a cop-out: full chords in fast passages are simplified this way constantly, even by players who could technically hold every note given enough time.
Which notes matter most
How to play it
Rolled slowly: bottom to top, landing and holding the top G, exactly as rolling-a-chord-with-the-bow taught. If there's no time to set every finger, the triage below tells you what to sacrifice first.
Keep the outer two notes: the bass and the melody top. They carry the chord's identity — the low G anchors the harmony, the high G is usually where the melodic line actually continues into the next note. The inner voices (D, B here) are the first to go when there isn't time to hold everything — treat them as quick passing notes the bow brushes through on its way up, rather than notes you stop to tune precisely.
Try it
Try
Play the chord above two ways: first, fully held, taking your time on every string. Then again, faster, deliberately loosening your grip on the inner two strings while still landing cleanly on the bass and the top G. Notice the second version is still recognisably "the chord," even though less of it is precisely controlled.
The usual mistake
Treating a rushed, half-formed attempt at holding every note as more honest than a deliberately simplified version. It isn't — a clean bass-and-top with a blurred middle sounds far more musical than four notes all fighting for a hand that doesn't have time to set them. Triage on purpose, don't just fail by accident.