There's a single integrated terminal structure now, so I don't think there are any shuttles. My experience was barely pre-covid, but I believe you will clear immigration and customs in BOG and enter the domestic side of the terminal. I do recall a notable walk in the catacombs, so to speak, from my arrival gate to immigration, but that all depends on the arrival gate. It's all quite well marked and modern, it shouldn't be a problem for any reasonably seasoned traveler.