V15 Cannot add a block to a group in a block grid editor

[nhudinh0309]

Which Umbraco version are you using? (Please write the exact version, example: 10.1.0)

15.2.0-rc

Bug summary

When the user tries to add a block to a group in the block grid editor, the new block displays at the top of the Blocks section instead of within the group.

Specifics

No response

Steps to reproduce

1. Create a block grid data type
2. Add a new block group
3. Add a block to the group

Expected result / actual result

Expected Result: The new block should display under the block group.
Actual Result: The new block displays at the top of the Blocks section, not within the group.

BlockGroup_Issue.mp4

[madsrasmussen]

Fixed by #18021