Thank you for the link to recreate a version 9 Styles tab-bar. You sure have a difficult job of diplomatically fielding questions and complaints. 
Please give me a couple examples of which v9.x features won't work on the current OSes? I am curious.
My new v11.17 is/was a new install on a new desktop. My old Opus 9.5 was on a laptop whose drive is lost amidst my collection of "replaced" drives--hard drives that were removed in place of newer and much larger capacity. I must have at least a dozen drives in sizes ranging from 4gb to 13gb (dating back to 2003 or 2004) to 1,500gb. If I can track down which drive the backups are on, then I will reinstall my old v9.5 setup.
Why was the Find utility removed from having a separate floating existence starting back in v10? I cannot fathom what the developers' reasoning could have possibly been. I saw (and read) one thread ([url]Float separate search]) where the thread posters bemoaned the removal of the Floating Find Utility, giving many reasons why they really liked its pre-version 10 functionality and hated its incarnation since v10. I read all 6 pages of topic=14056 and found I agreed with every one of each person's reasons for really liking the old floating Find and disliking the new permanent (well, new since version 10 I gather) implementation. I also add my name to that list of lamenters. I found the above thread by searching for something like "find window panel layout".
In any event, why was the floating capability of the Find panel removed after version 9.x? Also, why were the Styles tabs removed and the menus drastically reduced?