How to Create a Multi-Column Custom Content Element

I'm trying to create a custom two-column content element in Typo3 Neos. I'm aware that Neos is shipped with multi-column functionality, but for this particular case I need to create my own custom content element.

So far I've been able to create one of the columns (see below gist for code). However, as soon as I try to add the second column, the page just turns blank and no further changes can be made.

Gists

1 column activated (working properly): https://gist.github.com/anonymous/c5f33c7923faae26aa1a
2 columns activated (not working): https://gist.github.com/anonymous/85fc6994e9e2c5892a11

Any idea why that is happening, or how to solve this / build a multi-column custom content element in Neos?

Solution

I found the solution! I simply had to execute the following flow command to create the missing node: ./flow node:autocreatechildnodes --node-type Daniel.MultiColumn:TwoCol