I noticed I have multiple versions of Addon manager installed (screenshot).
No, you don't. You don't have "multiple Addon Managers", multiple entries in the Windows Control Panel only indicates there are multiple registry entries pointing to multiple ways to UNINSTALL IT.
This is usually a result of having removed some files by hand at some stage, instead of running the proper Uninstaller. Or, having run a dangerous registry "cleaner", that probably messed up things. I see dates from 2012, so this might have happened long ago.
If you have FS9, FSX and P3D, all in the same Windows installation, you should only see 3 Addon Manager Uninstallers there (again, please note that page is not telling you what you have installed, it's telling you what you CAN Uninstall! ), each one clearly identified as the sim it relates to so, you should see:
"Virtuali Addon Manager" ( FS9 version )
"Virtuali Addon ManagerX FSX" ( FSX installation )
"Virtuali Addon Manager P3D" ( P3D installation )
But having multiple entries won't cause ANY problems. It's just a cosmetic issue, the copy installed is only one in any case.
If you don't like to see multiple entries, uninstall them ALL, then reinstall all the 3 different version, FS9, FSX and P3D (FSX and P3D is the same installer, it will simply ask you the sim)
If you have the P3D Migration Tool, DO NOT USE IT, keep it disabled entirely when installing anything (all our products) that natively supports P3D.
Before installing a new addon manager am I supposed to do an uninstall first?
Won't make any difference and if it did, our installer would either force you to Uninstall first or it would Uninstall automatically itself.