Currently, the editor allows you to create a level with 11+ skills despite the 10 skill limit. It will warn about it when validating the level, but it still lets you save it with the excess skills assigned.
The player handles this gracefully by truncating the excess skills. But this creates a potential problem: In addition to resulting in some strange behavior when trying to modify skill allocations without exercising caution to ensure you don't exceed the limit (why is this skill I'm trying to add not showing?), if an eleventh skill is accidentally left in during development and hidden by the truncation behavior, these hidden skills could reappear if the limit is ever changed again.
I'd suggest graying out the fields for unused skills when the maximum number of skills have already been selected (by graying out only unused skills, this should prevent levels which have been manually edited to contain more than the maximum allowed number of skills from causing strange behaviors when loaded in the editor). To show that the editor does in fact save all the skills, rather than deleting the excess, a demonstration 1-of-everything level is attached.