Trading with the new ui got a little less flexible compared to before. When having a mount nearby, there's no option to purchase the trade goods into your inventory. If you purchase trade items with a mount in proximity, the items will automatically go into the mounts inventory. The purchase proceeds if your mount weight is <100% and you have inventory slots available. Your purchase order might be completed only partly "as it fits", i.e. up to 170% weight or all slots are filled. Only if you have no mount nearby you get the message prompt to purchase the trade items into your inventory. If I remember correctly this prompt happened with the old ui (not necessarily only) if you purchased items with more weight than your mount could carry. At least you could always make the trade goods be placed in the mounts inventory or your characters inventory. https://prnt.sc/piek8l https://prnt.sc/pielib