If you use bonemeal on Grass Slabs (and Stairs) it will have no effect. Is that an real issue or it is planed? I'm not sure.

Thank you for all your feedback and issue reports, however this one I most likely will not be implementing as my modding is on a very beginner level and this would probably require me to reimplement the whole bonemeal and grass/flowers functionality, which I simply don't know how to do. Maybe some day :)

You're welcome. Nothing to thanks.
Also me too - verry beginner - roundabout 6 months ago I've start to learn coding in Java.

My tests with Bonemealable Blocks works fine on Blocks, and three of my four Slabs (for Stairs I haven't coded it), but on the upper sided Slabs it looks ....

a lil bit crazy.

My idea was: creating my own ModDirtSlabBlock - Class

public class ModDirtSlabBlock extends SlabBlock implements BonemealableBlock {

Why it will not work on one of my own slabs... I don't know.

You've got a private message on CurseForge....

OK, Bonemeal on Dirt/Grass-Stairs is not the best idea. Unless the plant will be shrink a bit and will span an the right level ;) ;) ;)