Nice, but for which exact jdev version you developed this extension?
Is the extension developed with extension development kit for JDeveloper? If so, "Please post a new thread on the discussion forum if you'd like to upload your extension to this page." , which would be this thread if extension is accepted.
I used 184.108.40.206.0, but it might work in older 12g releases as well - would have to check that. I assumed that as 12.2 is older than two years, it is not necessary to support older versions.
Extension seems to be working to some degree in SQL Developer 19.2, but it's not very useful there.
I installed JDeveloper 11g and extension doesn't work there, as extension is compiled for Java 8, but I'll try to compile version for it.
I'm not enough familiar with JDeveloper to know which versions are in wider use, so let me know if I should focus on particular releases.
11g uses a different extension model. Not sure if just recompiling will do.
12c has some differences between versions. That s the reason I asked for the exact version number. I'm not sure if you can add an extension built with 220.127.116.11 into 18.104.22.168.
I released new version (0.2.0.1) with two variants:
12c (12.2.1 or greater, but requires Java 8)
11g (11.1.2/11gR2 or greater)
Tested it with few versions and it should more/less work.