For the past few months I have been working on a new app. Its goal is to eventually replace all the current tools (all editors and the custom leaderboards recorder) and include a lot of QOL improvements. The new app is cross-platform will simply be called ddinfo-tools.
It is currently in development and an alpha build for Windows can be downloaded here. A Linux build will be available later if anyone wants to help test it.
At this point, only support for custom leaderboards has been fully implemented. There is also a working survival editor (still a work in progress) which includes some new stuff as well, such as a 3D editor, full undo and redo support, more editing tools, etc.
As always, the code is open source and can be found on GitHub. For more info, check the tools page.