Ability to Adjust Volume Level of the Headset Connected to Dualshock

My PS4 Pro is connected to my Samsung 46D7000 which is old but still a very good tv. Unfortunately it doesn’t have native Bluetooth capacity, so it’s a bit of a problem to play games and use Plex to watch movies at night. So I connect my Sony MDR100ABN/B headphones with the stereo cable to the Dualshock controller and here comes my problem; I cannot adjust the level of the volume coming from the controller neither with controller nor using the Plex app. The manual volume adjustment buttons on the headphone do not work either. So the sound is maxed out. There is a level for this in the PS4 menus but it’s so deep and not practical.

So, would you add an option to adjust the volume level inside the Plex app please that we can play with the controller while watching something and when it is too loud we can adjust the volume? I think the touchpad on the controller would be very useful for this.

Thanks in advance.