Hello I am new here,
How can I make the sidebar larger and the main area smaller? Let's 60/40 ratio for example.
I think it would be great to make CSS editing easier.
Hi @Youssouf_Ouologuem Welcome!
Currently, we don't have native support for configuring the sidebar width 
We have a feature request for tracking customer use cases for configuring the sidebar width so I'll add your +1
We're also tracking requests for easier ways to implement css. Currently, it's very tricky to set up and difficult to maintain, so we recommend only using it when absolutely necessary.