New "Meta" Tile on Start menu: (see image) Anyone seen this?

Hello, everyone. I'm happy to find this very robust community of Win10 users. I hope someone here has some insight into this windows "feature", which doesn't seem to be documented or commented on anywhere online that I can find - possibly because I am not using the correct term for it -- although I've tried many.

Cut to the chase:
I've reorganize the start menu tiles and tile groups. All good. -- However -- after moving some tiles around, I noticed two of the tiles were missing and a new tile appeared (circled tile in the following image):
Attachment 153165

Clicking on it made a sub-group (for lack of a better term) of tiles appear below the tile group. The sub-group contained the two missing tiles and the new type of tile contained a "collapse" icon (i.e. "^"):
Attachment 153166

Trying to reproduce this, I found the following:

1. This occurs when one tile is dragged and dropped on another (sometimes - see point 2), upon which both of the tiles are placed in the subgroup and a new "meta" tile appears in place of the tile which received the dropped tile.

2. Dropping one tile on another is vexing to say the least. Most of the time (in 19 out of 20 attempts) the tile you attempt to drop it on just squirts to one side or another. You keep trying and eventually the tile underneath expands slightly instead of slipping to one side; dropping the tile at this point produces the results seen above. I suspect the way you hold your mouth may have some effect on your success at this.

Questions:
- Does this feature have a name?
- Is there a better way of using this since my method is a bit frustrating to use?
- By using this, did I cause Windows 10 to start a countdown sequence or chain reaction that ends with my computer going thermo-nuclear, destroying my desktop background image collection along with half the county?

Any suggestions or hints appreciated.

Ah... It has a name. Thank you, and I am glad to learn it isn't some obscure experiment at MS that will be corrected in a future update.

Given how difficult it is to drop one tile on another (still trying to figure out if sticking my tongue out or holding my breath works better when dropping the tile), I am a little surprised there isn't any easier way to create these.

Thank you for cluing me in.

Minor Addendum: The reason I had trouble creating the active tile folders is that all my tiles are Small. Resizing the tile you are dropping others on (Medium or larger) eliminates the problem of it dodging out of the way.

Caveat: be careful moving Tiles around, could end up unintentionally moving 1 to 4 or more onto another.