Would it be possible to add a feature to the custom columns preset which could set the size of the pane in which the preset was loaded or maybe maximize it?
IIRC this was already requested some time. In addition, remembering pane size would also useful for thumbnail mode (this was also requested already). I don't know if there are any plans according that, but I'd appreciate if that could be added.
When I need more space temporarily for custom columns, I switch TC window to vertical panes (Main menu: 'show' -> 'vertical arrangement'), maybe this could be a workaround for you too...