First of all, i'm huge fan of yEd and it's brilliant for learning and exams preparation. Keep up this great work! Wish you best of the best!
Second, some feautures just ask to be implemented into program.. They can introduce truly advanced system in yEd which is closer to mind and more interesting to use.
From easiest to hardest:
- Arrow split\joint system. Now you can do it with dummy split object, but native support of this can be very interesting.
- Arrow betewwen equal level objects; Now you can only have parent-child native relation, which is far from all possible relations between objects.
Simple way to introduce them is to add unicode symbols panel. It will be extremly usefull, and not that hard to create. Unicode have lots of them already: superscripts, subscripts, Greek symbols, integrals, summ symbol etc etc. Probably only thing which Unicode does not good enough is subscripting. I'm clearly asking too much, but customisable symbols panel with categoryes+ sub +superscript can introduce great math into yEd.
We can clearly separate some types of system: Object, operation, property. Probably others. Yes, you can do this with colors now. But it would be great if program could understand them a bit more usefully, since right now any instrument goes to obhect-arrow system, which starts to be not enough in any advanced scientific or programming diagram. For example, if object have properyes, like color, metric, etc, these propertyes are hard to put properly into diagram. Even harder to propose right way to introduce these feautures, but it's good direction to attempt for.
Multi-dimensional graphs is another very interesting concept. Now any object have only XY, it's realtively easy to add Z and overlapping, probably much harder to add infinite dimensions and projections. Still, just Z can became very unusual instrument clearly fun to use and research!