Not sure if I remember this correctly anymore, I believe any hotbar that is not your own is considered as the Other/Mount hotbar for PS4 controller users, so you must allow these hotbars to replace the Cross hotbar. But if you switch hotbar to hotbar 8 and then back, you lose that hotbar on your Cross hotbar since it isn't mapped to the Cross hotbar (we only can select Cross hotbars 1-8). You can't copy the actions over unfortunately. I've always just enabled the setting "Automatically replace cross hotbar 1 with pet hotbar when mounted" after I had a similar issue in the past. Hope this helps.