Constructors for user types should probably be part of the config section

The constructor block is weird: it's not an expression, and there's really only one block that can go there, but you still have to hunt it down in the toolbox.

Instead, the constructor name and number of type parameters could be added to the config block. I guess the problem there is that it requires a non-trivial layout for inline blocks. So this is probably hard, but I'll leave the feature request open anyway.

Start by locating the toolbox's constructor block and the config block that would contain user-type settings. Determine how inline blocks are laid out and what existing tests or examples cover these blocks; done means the constructor name and type-parameter count are available in the config section without requiring a separate constructor block.

Written by the indexing model from the issue text.