Toolbar Editor: Default to a bigger dialog size (Issue #758)

The dialog is too small because it has too few buttons on the right and it was setup like the column editor.
To deal with it we could either:
- Create a complex setup of boxes.
- Manually set a top-margin for the `Default Order` button.
- Set the rows to homogenous, which I did. The downside of this approach is that it makes the separator huge, so I removed it.