For the standard user it would be most useful to have the capability of ordering the icons in the toolbar to suit our own specific use, via the customise icon GUI.
I have other editors that I use more frequently and it would be good to have the icon order in RJTe to match those other editors. A the moment you can enable individual icons at will and make some of them appear on either of the two toolbars but it would be most useful to be able to order them within a toolbar to suit a particular use.

The image above just shows some additional buttons added to change the order of the icons as they appear in the list. I feel the vertical placement of the icons in this GUI is a little misleading, so the icons have to be moved up/down in the list when it really ought to be right/left. However, changing the orientation might be too much of a change.
I'll leave it to you to figure out. A useful improvement I feel.