Hi, that's very interesting, thanks. We are looking at modifying Eclipse JDT to add such things as a reverse-continue button similar to that in CDT
That would be a great addition! I think you'd also need to add this feature to the generic Debug framework (eclipse.platform.debug) for best results and more factorized/shareable development.
and wondering how important/easy it is to target IntelliJ as well.
It depends on your target audience and the long term strategy for your development.
DISCLAIMER: the next paragraph is based on a non-objective, personal and biased opinion and shouldn't be trusted. It's just one narrowly-minded POV, and in no case a piece of advice for your succes.
I personally wouldn't bet much on IJ on long-term. the fact that it's a single-vendor development behind it and that VSCode is successfully attacking many market segments which are major revenue fountains for the developers of IJ may at some point have an impact on the sustainability of this product in term of funding. Eclipse IDE, on the other side, since it's community multi-vendor open-source, is more sustainable; one example is that it already faced a major competition -when IJ grew in the last years- and saw its marketshare almost divided by 2 but it's still alive, rocking and even growing and innovating. That's the beauty of real OSS!