Note it appears to be VERY sensitive to the placement of the ending };} sequence
It can appear to work but then you can't save or you can save but then can't load the project back in
whenever I try to put a "function" in the input slot options, I can't update the custom block, like the apply button doesn't work, and the ok button doesn't close the dialog, and doesn't update the block.
and I apparently can't change the block shape, or the category.
edit: I just found out that the ok button and the apply button do update the block, they just don't update the parameters if they have a menu, or default value.