Using the % sign is a very old and finicky way of linking the blocks up. If you look at newer extensions, you’ll see how you should be doing it with the $ sign. And how to use
//% sprite.shadow = variable_get
//% sprite.defl = “mySprite”
I do not remember if this is the correct syntax. You’ll have to look at a newer extension. It might be variables_get or get_variable, idk.
Also, if you want to put things into the sprites tab, you can just use “namespace sprites” without all the “//%” stuff and they will be added. All that stuff only needs to be defined once per namespace, so just using the sprites namespace makes it a lot easier.
You can look at my extension Making an extension for every JavaScript exclusive feature I can think of! for an example of a newer extension.