1 block by layout column

Hello!

I am building a layout field with custom blocks for a layout on the front.
It all works fine. However a details annoy me in the panel.

Right now, the client can make the mistake of adding a block to a column that already have a block such as this:

It is a problem for the front-end as it renders fine anyway, but it mess up the presentation of the panel.
(Note: I made a tweak and reduced the opacity and filtered grayscale the block:not-first-child sot hat we see visually that there is an issue.)

But technically, how could I make it easier for the client and only give the possibility to create new row of columns and only drag in empty column-cell?

Clean version:

Thanks! :smiley:

You could set a max to the block field

I don’t know if this here is still functional, but looks like you could limit number of blocks per column with it: