Creating Managed Properties isn’t difficult. The real challenge is to keep track of all custom Managed Properties. Although SharePoint 2013 allows you to export search configuration, it only allows you to do so on the Site Collection level. Unfortunately, as you can only create Managed Properties of types Text and Yes/No at the Site Collection level, you will find yourself creating custom Managed Properties in Central Administration where there is no easy way for you to see which of the few hundreds Managed Properties belong to SharePoint and which are custom.
If you have access to PowerShell, you can easily get a list of all custom Managed Properties using the following snippet:
$ssa = Get-SPEnterpriseSearchServiceApplication Get-SPEnterpriseSearchMetadataManagedProperty -SearchApplication $ssa | ? { $_.SystemDefined -eq $false } | ft Name
One thing worth mentioning is, that the list that this script produces, contains both Managed Properties created manually and Managed Properties created automatically for your custom Site Columns during a Full Crawl.
