Reducing Number of Columns Deletes Content

[mrwweb]

Describe the bug
When creating multiple columns and then reducing the number of columns by one or more, the blocks in the removed columns are lost.

To Reproduce

1. Add a columns block of 3 or more
2. Fill in all the columns with content
3. Reduce the number of blocks (right column disappears)
4. Increase the number of blocks (right column is empty)

Note: The content is recoverable using undo, though there's a smaller bug where the addition/removal of the column and the incrementing of the column number setting textbox are two separate steps of undoing.

Expected behavior
I know that the current behavior is not what I expect, but I could see a variety of acceptable behaviors.

1. My initial expectation was that the columns would act as a grid. i.e. I have 4 columns of content. If I reduce the columns to 3, I will have one row of 3 column and 1 row of one column. When I later showed this bug to a fellow WordPress user he independently shared the same expectation when I asked him what he expected to happen before I reduced the number of columns.
2. A second thought was that the removed column might simply just be removed from the columns and placed directly in the body below the columns block. This might be a little weird but would avoid the data loss.
3. A warning that I am about to lose data. Possibly provide the option to place the lost blocks below the columns or confirm deletion.

Screenshots

Desktop (please complete the following information):
Win 10, Firefox 63.0.3, WordPress 5.0, no plugins, Twenty Nineteen

[youknowriad]

I think this needs to be improved design-wise. Ideally removing a column is an explicit action (clicking a "x" or something like that) instead of a range input.

[msdesign21]

Related: #9009

[youknowriad]

Thanks @msdesign21 Let's close as a duplicate of #9009