The 'Add on Manager' was placed in C/Program Files(x86)......can I move it to the G/P3Dv5 (flight simulator)
Installing the Addon Manager in the simulator own folder is probably the worse possible choice for a destination. In fact, LM reccomends a proper P3D product should NOT install *anything* in the simulator own folder and, even if some developers still do it, it's a sensible suggestion, which is why our installers comply with that.
Also, consider our installer shares a lot of files between different versions of the same product running on multiple simulators, for the obvious reason to not waste space with duplicate files when using multiple simulators so, installing something "inside" P3DV5, would be very confusing if you later on switch to MSFS and found all the FSDT add-ons for MSFS inside a P3D5...
The default install in C:\Program Files(x86)\Addon Manager is perfectly fine and, the only reason you would want to change it, is if you are low on space on the C drive. In that case, choose something else like D:, E:, F:, etc. but not the simulator folder.
