This feature will be included in the next major update of the mobile version which is the priority we are currently working on.
In general, why doesn't the toolbar at the top/middle of the screen appear in the Android version of Viewer as it does in the Windows version of Viewer?
Not all features can be implemented the same way as they exist in the desktop version. Yet, we will do our best to include as many important features in the mobile update as possible. One of them is a full-fledged address book compatible with the desktop Viewer's address book.
There is the current stable version 184.108.40.206 available from the regular download page, and a new beta version. In a few days we are going to roll out the final 6.9 release and this new version will replace version 6.8.
Unfortunately, we do not provide earlier versions. We always recommend that you use the latest version, on both sides (Viewer and Host). Otherwise, we cannot guarantee that the bug you may encounter is something new and not just a known bug that is already fixed in a subsequent update.