Thanks for porting the mod to Minecraft 1.12. :)
I am currently testing out the mod and so far I have noticed that Growthcraft items appear everywhere in the creative menu:

As you can see Growthcraft items beginning from the White Crowbar to Ricotta Curds appear everywhere. It could be caused by getSubItems now being called by all tabs.

Fixed in recent release published on Discord. It will be published on curseforge, soon.