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My one criticism of them would be they focus very heavily on cloud, and their on-premises offering is woefully anaemic, lacking fundamental functionality, such as messaging.
Don't worry about the code looking dirty, embryonic code always does. If it's a big enough tool it may warrant setting up a GitHub Pages site for it, just to make it a bit easier to find when somebody is suffering from the same problems you were.
In terms of new features, once you've put the repo on GitHub (or wherever) other people will likely suggest features as issues or modify the program themselves (and hopefully open a PR).
I've seen bugs that user's don't notice.
I've seen bugs that user's have just gotten used to.
I've seen bugs where that failures it caused were dismissed as the system being a bit temperamental, for many years.
I've seen bugs that financially affected thousands of customers, and remained unnoticed over the course of several years.
I've even seen bugs that only remained because, by luck, the preconditions to trigger it had not been met.
I can assure you, you do find bugs in legacy code.
I'm not sure if you're managing a project, product or divisional team structure, but I would say that no matter what level you're attempting to manage, set some sort of vision for your team to align themselves with. This can cover things such as technical aspirations, or organisational strategic goals.
Trust your team. It doesn't sound like there is any mistrust in your team, but I understand the difficulty in getting over that initial knowledge hump when introducing people to a new domain, especially as an "expert" in the area. Documenting knowledge in clear and concise ways, and making different members of your team experts in certain areas of your knowledge will help them to become more self-sufficient in their quest for knowledge and answers. Consider this an investment.
As a general piece of advice, not aimed at any particular part of your post, you were in the same position as your team members are now not long ago, think about the pain points you had and try to learn from them.
This is a product I REALLY want. Since I want to be able to diagram entire complex systems without always seeing 10,000 boxes on screen. You could start a presentation at 35,000 feet, showing the entire rough structure, then zoom into different regions where more detail will appear (infinitely)
Nestable feels more like excalidraw, with a folder/file structure?
[1] https://contexts.online