Hi. I actually have quite solid experience making level editors for DOS tile-based platformer games. Some of you might remember, that about 2 years ago, I created level editors for
Hocus Pocus and
Vinyl Goddess From Mars.
The editors are made in Delphi 7, which is development toolkit based on Pascal programmig language. Delphi 7 is really outdated, but still it's, at least for me, the easiest way to create Windows GUI programs. Some more modern tools, like Qt, I find much more complicated and difficult to use, but that's rather about personal preference and experience.
To be honest, these two editors are not my only level editors I made. Many years earlier, about 2010 or 2012, I started creating a
map editor for strategy game called Dune 2000. The UI as well as features went through long development and improvements during the years. Eventually the editor became really superior and powerful tool with features that can extremely ease creation of the maps, and was used by many people to create even hundreds of new maps and several full custom campaigns.
Then I got eager to create a level editor for another great classic game, which was lacking a fully functional level editor for many years: Hocus Pocus. I discovered the Modding Wiki and found out, that all the level format of Hocus Pocus was already reverse-engineered, and some attempts to create level editor for this game already happened, but none of them were fully usable. I challenged myself to create an user-friendly tool which can edit all the parts of the levels, including switches, locks etc.
Basically half of the work was already done, because I just took the source code of Dune 2000 editor as a base for Hocus Pocus editor, and re-used many parts of it, mostly the program "skeleton", user interface and rendeding and painting routines. What I needed to do, was to implement loading and saving levels in Hocus Pocus format, loading the tilesets and later sprites, and implement new UI for Hocus Pocus-specific level objects, like switches, locks etc. The level minimap feature is inherent from a strategy game, but appeared to be a great and innovative feature in a platformer game level editor, and I've probably not seen that in any other editor I tried, even Abiathar. One significant new thing I implemented in Hocus Pocus editor was the Pattern editing mode, which is very suitable for such game.
After success with creation of Hocus Pocus level editor, I wanted to create an editor for my other favourite childhood game: Vinyl Goddess from Mars. And here, I started off taking Hocus Pocus editor as a code base (which saved half of the work for me once again), and rewriting routines to load/save the levels and creating UI for VGFM-specific features. Creating VGFM level editor was much fun for me for the reason, that the level format was only partially reverse-engineered and documented on the Modding Wiki. I needed to reverse-engineer big part of the level format on my own. Which was really fun and satisfactory, because it felt like an adventure. Unlike in Hocus Pocus case, this time I also created a few full custom levels.
I was also seriously thinking about creating a third level editor in a row for another game I liked as a child: Jill of the Jungle. I was well-experienced with previous games, and the Jill level format was pretty well described on the modding Wiki, so it looked like another great challenge for me. But unfortunately, that did not happen, and I got disinterested and never even started making Jill level editor.
The main reason for this was lack of interest of modders to create some new levels and mods for either Hocus Pocus or Vinyl Goddess from Mars. In short, I did not get what I was expecting and looking forward to: new levels and mods for my favourite games I could play and enjoy. While the earliest Dune 2000 editor was heavily used to create numerous mods and whole campaigns (which got published too), the Hocus Pocus editor was barely used by a few most interested Hocus Pocus fans to create two, or probably three new levels, which they really published and I could play. For the latter VGFM editor, I got practically zero outcome, with my own custom levels being the only existing new levels for this game. And to make things worse, I unintentionally caused a flame discussion in the VGFM level editor thread on this forum. So in the end, I realized it's probably too late (about 25 years after publishing these games) for level editors to be worth being created, as the games no longer have community and modding base strong enough to create any serious mods and level packs for these games. And I directed my interest in completely different things.
Back to the technical topic. Technically you could just take source code of either Hocus or Vinyl level editors, and rewrite it to support Jill of the Jungle. But that's practically impossible to happen, as you most probably don't know either Delphi or Pascal, and are not familiar with the source code of the editors. But I hope I gave some useful or at least interesting information to you, and made some philosophical question whether it's even worth investing time and effort into something what barely somebody would use. You could give your opinion about that.