I have been scanning through the forum (maybe ineptly) & found a recommended solution of re-installing plug-ins from command center. I did this & am still not seeing the Sonitus:fx compressor presets I enjoyed on the old machine w/ Sonar x3. Can someone help me find the presets, please?

Try looking in C:\Program Files\Cakewalk\Shared Plugins. They are .ini files, e.g. FXCompressorDX.ini.
 

Thank-you, Adrian! I will give this a try.

Ran into the same issue. Discovered that to access the presets, there is now a button called "Presets" on the UI. It's on the right hand side of the plug-in when the UI comes up. Preset access used to be in the main window up top with the drop down arrow.

Right, this UI change confused me the first time I saw it. I always meant to post a query about it here but it faded in importance.