This is pretty self-explanatory.
Search bar so you won't waste time reading every single block in every single category just to find the needed one.
Also, on the side note, I can't find play sound proc.block.
Issue comments
It is in the world procedures category.
I suggest you check our tutorials collection playlist on our YouTube channel which contains many examples and tutorials that can help you get started with MCreator: https://www.youtube.com/playlist?list=PLAeL-oIFIEngE6jRgFYeFMfuj8WQsO3Ei
Some good news: https://github.com/google/blockly/pull/1066#event-3139196073
We just need to wait for this feature to get in a release. I am re-opening this ticket as now this feature is closer to being possible.
Related, duplicate: https://mcreator.net/tracker/issue/65592 (also proposes sorting type selection)
We use Google Blockly for the procedure system. We are waiting for them to implement a search system. You can monitor the progress here: https://github.com/google/blockly/issues/766