[jackie_w]

Yes. I've used a fairly similar structure for all the Editor plugins I've done. Summarised below.

Once ResultsDlg (and optional Show Diffs dialog) are closed:

• With red bit - all tweaks show in Preview/LiveCSS, no highlight, all OK.
• Without red bit - all tweaks show in Preview/LiveCSS, but highlight also still visible in both, but not in Show Diffs.
  Double-clicking CSS file (as long as it wasn't already open) makes highlight disappear.

Spoiler:

class CSSTweakerTool(Tool):
    name = 'CSSTweaker'
    ...

    def create_action(self, for_toolbar=True):
        ...
        ac.triggered.connect(self.do_the_action)
        return ac

    def do_the_action(self):
        self.boss.commit_all_editors_to_container()
        
        try:
            show_changes, dirty = self.css_tweaker()
        except Exception:
            import traceback
            msg = 'Failed to Tweak CSS file'
            error_dialog(self.gui, _(msg), ...)
            self.boss.revert_requested(self.boss.global_undo.previous_container)
        else:
            if show_changes:
                self.boss.show_current_diff()
            if dirty:
                self.boss.apply_container_update_to_gui()
            else:
                self.boss.rewind_savepoint()

    def css_tweaker(self):
        log = []
        self.boss.add_savepoint('Before: CSS Tweaker')
        container = self.current_container
        
        ... find container cssname ...
        ... some container checking ...
        if not OK to proceed:
            return False, False

        dlg = CSSTweakerDlg(...)
        if dlg.exec_():
            
            try:
                self.boss.close_editor(cssname)
            except:
                pass
            self.boss.edit_file(cssname)
            
            log.extend(dlg.csslog)
            resdlg = ResultsDlg(self.name, log, show_changes_button=True, parent=self.gui)
            return resdlg.exec_(), True
        else:    
            return False, False

ETA: Extra info. I should have tried this sooner - without the red bit I can also "fix" things by right-clicking Preview and selecting 'Refresh Preview"

ETA2: Replacing the red bit with the single command you spoke of above, self.boss.gui.preview.start_refresh_timer() also fixes things. This is neater.

In the production version of 2.62 adding that command twice, fixes things:
1st - where the red bit is
2nd - immediately following the self.boss.apply_container_update_to_gui()