heya! yes, an oversight on my part! will be added soon, hopefully by the end of next week at worst. In the meantime, you can load the second model as a live2d item by dragging the models folder directly into the program while another model is loaded
If you need further explanations for that, check out our discord server and we will try to give you a better hand there https://discord.gg/cCXksNG8fY