Z-index ordering for canvases

While creating quite large UI for my game I decided to organize parts of it in separate canvases more than not for logical separation. It worked fine up until new popup that needed to be created. My new canvas is rendering at the z-bottom. Sibling index is not changing order of rendering (Move Front/Back options on rect transform nor drag drop on hierarchy). The only way I found that works is by editing sceen .unity file and moving appropriate Canvas: section closer to beginning of file.

• Is having multiple canvases a bad practice?

• If not how to z-order them from editor?