Technically, I suppose I don't need to.
I currently have several DSL scripts categorized in different directories that configure ~145 jobs. My current seed job had a build step for each directory (some of these directories are all DSL scripts - others contain groovy files that get read into the DSL scripts.. so i would have to write a more complicated regex for which files to process that i felt was necessary when i could just use multiple build steps).
This was something I noticed that I felt should be brought to your attention - but I guess isn't a blocker.
Sounds like it should be handled in Jenkins core anyway - thanks!
I can reproduce this on 1.642.1 and on 2.32.1.
The fields will appear if you click on the radio buttons. The script text will appear if you start editing. I think this is a framework bug in Jenkins/Stapler/Jelly and needs to be fixed there.
The issue with multiple links in the sidebar is also a limitation of the framework and would IMHO need to be addressed in Jenkins core. A build step can provide some actions to be shown in the side bar. And Jenkins currently shows all provided action even if they are identical.
Why do you need multiple Job DSL build steps?