But in this case I'd like to ask (as always) ;-)
- "... what do you need that for?"
- "... would not a database be the better storage-approach for complex data?"
It defines a graphical element with a possibly complex sequence of properties.

I find a sql database is good for only very simple structure. I worked as a db developer for seven years. I know what a pain sql is when dealing with greater than four table joins. It's quite ugly, ridiculous and unwieldly. In this case especially, the structure IS hierarchical. In it's sql form, it's nine tables - for one object.

I am surprised enums are the problem. On some very simple tests I just did, sub-types and arrays do seem to work.