I appreciate why two-levels of saving became necessary when editing a T4 template's style. It does add another level of complexity to the user interface - more clicks are needed.
One way to minimize the number of clicks and be quite a bit more user-friendly is if a click anywhere in a user panel that is not in edit mode, when testing whether it is in edit mode, instead of displaying a message that editing needs to be enabled, just directly places the panel in edit mode and then allows the default action of the click to take effect. I do not know of a use case where a user clicks in a panel and does not intend to be in edit mode, so lets just solve the issue and take two actions based on the one click - set edit mode to on and execute whatever they clicked on. This will be a significant improvement in user friendliness - helping them get to their goal without needless interruption. If they did not intend to start an edit, they can always cancel edit mode / not save template changes.
Similarly, once the user is done working in T4 and they have their last accordion panel still open with unsaved / not previewed changes, that if they click the big template "SAVE" button or :"SAVE and CLOSE" button option, that it commits any unsaved changes in the displayed/edit mode panel followed by committing the save of the entire style, all in one click. If a user has gone in to make a change that they are highly confident they got it right without needing to see a refreshed preview, let them use the big SAVE button to commit all changes and exit the editor as efficiently as possible.