I'm not disagreeing with you that Dear ImGUI is not at the same level as Qt for an end-user app but if you want to make a visual tool for creating UIs in ImGUI

I'm not disagreeing with you that Dear ImGUI is not at the same level as Qt for an end-user app but if you want to make a visual tool for creating UIs in ImGUI there is nothing stopping you. You write some tool to walk over your description of the data and call the correct functions. Nothing hard or special about it.