Ignition GUI question: can I add my model to a running simulation?

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Hi, I'm running the ~latest Ignition Gazebo built from these instructions: https://ignitionrobotics.org/docs/gar...

I'm learning how to use the GUI, build models using sdf, etc. My development method is "make a change to an sdf file, and restart the simulation to see what happens." Is there a better way to see a change to a model? I see in the Entity Tree widget that I can use to add a few standard shapes to a running simulation, but I don't see a way to get my models into that list. Is that possible?

Thanks!

P.S. -- if there are any cheat sheets or tips & tricks posts, please let me know.