Thanks for the helpful feedback. I did not think the whole thing through but my pipeline idea would be :
Create Template Config File → Save as JSON (contains field name, default value and limits/options)
Create Config File → Open existing Template file → Set values → Save as a Dict (where field names are keys) in JSON.
The config file can then be directly fed by being read as a Dict.
In short it is simply a practical (?) config file GUI maker 
I advanced a bit more to make things maybe more clear
For the code it’s pretty ugly so far but you can still check it out if you want :
https://github.com/theogf/MLExps.jl
As you see I was going in the same direction as you did. You can simply check src/gui_config.jl and test/test_gui.jl