Also it would be really cool if there were a group tab where you could see all groups (and also name the groups so they aren't just Group_XY).
The group tab should display all groups where you can rename them or select all the blocks within that group. Additionally, on export there should be an option "[ ] Merge groups" which works kinda like merge blocks but doesn't merge all blocks into one but merges them based on groups so that when you import it into an engine or blender you have one object per group.
Then the group tab should have some "expand" arrow where you can expand the group to get a list of all the blocks within that group and allow you to select an individual block of the group. reason is that once you have grouped something but then need to copy/paste a block from the group you have to ungroup, copy/paste it, and then you have to re-group again which is just a lot of clicking.