is there somewhere I can contribute finished problems as examples?
Yes, please! https://github.com/JuliaOpt/JuMP.jl/tree/master/examples. Please pay attention to the structure of the existing examples: they get run in JuMP’s automated tests. (You can run the tests using this command https://github.com/JuliaOpt/JuMP.jl/blob/fd5ea00cb602145b677c136295b07cab6791f1b0/examples/run_examples.jl#L12)
I spent a lot of time clicking through the JuliaOpt notebooks page but it seems like they are written using pre 0.19 syntax.
We will have some news to share on this front soon.