Editable Tree Model Example - Minimizing arrow can be hidden by columns

Description:

If the amount of children is sufficient, the arrow that represents that they are children can be hidden by the start of the column. The text is then hidden, behind the next column.

Steps to reproduce:

1. Open the Editable tree model example
2. Add children in a column until their "level" is hidden by the next column

Expected behavior:

The "level" in the tree should not be hidden by the next column. They should always remain visible as it can confuse navigation in the tree.

Observed behavior:

The "levels" are hidden if there are sufficiently enough children in tree.
Special notes:

The following column could be pushed back so that no text is hidden for example.