I can not answer you question, but you link to Causal.jl is broken for me.
Fixed the link to Causal.jl, I hope, thank you.
The Modia folks started a GUI: [Feature request] GUI · Issue #95 · ModiaSim/Modia.jl · GitHub.
See also some interesting hints from Chris in this interview: Simulations are about to get way, way faster with JuliaSim.
@tshort your first link is a feature request from 2019 and it seems still unresolved…
Your second link about JuliaSim is also outdated ;-). JuliaSim is already out but it is not clear to me whether a) it has a GUI and b) it will be available to non-paying entities.
The GUI part is still under development, it will require a license but we will work with academics and students to provide it at a reduced cost.