Could have (-(y)abilirdi)

In the world of filmmaking, hindsight is 20/20. To talk about missed opportunities and alternative outcomes—things that could have happened but didn't—Turkish combines the ability suffix -(y)abil / -(y)ebil with the aorist past suffix -irdi.

Verb Stem + -(y)abil / -(y)ebil + -irdi + Personal Suffix

The producer could have chosen a different cast.
Yapımcı farklı bir kadro seçebilirdi.

Notice how seç (choose) becomes seçebilirdi (could have chosen). The structure shows the alternative outcome was possible but ultimately did not happen.

To say "they could have," insert the plural suffix -ler, forming -(y)abilirlerdi or -(y)ebilirlerdi.

The footage was very dark, they could have used better lighting.
Görüntü çok karanlıktı, daha iyi bir aydınlatma kullanabilirlerdi.
They could have released the trailer before the theatrical release.
Fragmanı vizyondan önce yayımlayabilirlerdi.

For "we could have," use the first-person plural past ending -k, resulting in -(y)abilirdik or -(y)ebilirdik.

We could have added more effects to the trailer we prepared.
Hazırladığımız fragmana daha fazla efekt ekleyebilirdik.
Even if the dubbing were bad, we could have made a better box office gross.
Dublaj kötü olsa bile daha iyi bir hasılat yapabilirdik.