Does sitting with those who mock God's verses, and disapproving in one's heart while being able to disapprove verbally but neglecting to do so, constitute disbelief like theirs, as stated in His Almighty قول (saying): "Indeed, you would then be like them"?

Disbelief applies to whoever approves of the disbelievers' disbelief. As for someone who dislikes disbelief but sits with them, he commits a sin if he has no valid excuse for sitting without denouncing their actions. This is because whoever does not avoid people of sin has approved of their actions, and approval of disbelief is disbelief, based on the verse: {then indeed you would be like them}. Being like them is in sin, not in disbelief; thus, one becomes like them in committing sins. Therefore, he must repent to Allah and be elevated by his faith, strong and courageous.