I don't think it's fair to call it abandoned - flowcharts were last updated just 2 weeks ago in r437.
A problem we often have with feature requests is for any one feature, you can go down a rabbit hole of endless improvements and sub-features. Take effects, instance variables, the Platform behavior, functions, the Animations Editor, 3D Shape, etc. - for any of those and pretty much any other feature you can think of, someone could ask "is this abandoned? it doesn't have XYZ which is absolutely essential!" Really the question is, with our limited time and resources, does it generally do most of what most people need from it? Every individual user has a different set of requirements, and so no specific feature will always do absolutely everything that every single person could ever possibly expect of it.
As ever it's also sometimes hard to understand what people mean, and people often request things that are already possible. The feature request guidelines are there to try to avoid these problems. For example in brief my feedback would be:
- Load and save what? Do you mean the runtime state? Or the data of which nodes you have? Or the format it's saved to the project (which is actually already JSON)?
- You should already be able to detect a dead end by comparing if the output count is 0
- It's not clear to me why you'd need this or what specific problem you're trying to solve
- Again it's not clear what problem you've had here and whether something else can solve it
Resolving these issues can end up taking a great deal of time and energy - so much so that our policy is generally not to respond to feature requests, because we get so many and it takes so long to discuss them, that we just don't actually have time to do that. So really I'd encourage you to look at the feature request guidelines and try to always follow them when talking about features. These could also all be submitted individually to the feature request tracker if they haven't been already, with full details about the request following the guidelines - that's our process for this and it means these issues can be dealt with individually more clearly than usually happens on the forum.