Custom coordinates can be added to the MyCoordSysDefs.fme, which is located in the install directory FME\\Reproject....i.e. C:\\Program Files (x86)\\FME\\Reproject\\MyCoordSysDefs.fme. You would add the projection information below "Examples end here". More info here: Adding a Custom Coordinate System (safe.com)

@arryl​ Thanks for your question! We now have an interactive web site that lets you define custom coordinate systems using a convenient web form, available here. It lets you start from an existing FME coordinate system or the WKT from an Esri coordinate system, and will download the coordinate system to your computer. You may have to re-open FME to use the new coordinate system.

Hello Evie, I have tried adding a custom coordinate system using the web form, and downloaded it afterwards, it has given me 2 directories in a zip file namely: CoordinateSystemExceptions and CoordinateSystems, extracted them and placed in FME directory, re-opened FME but I am not able to reproject using it, shows the error ERROR |Reprojector (TeeFactory): Reprojector: Reproject: Could not reproject the geometry of the preceding feature: Unable to initialize coordinate system structure for coordinate system
 

Hi ​@bhavyagandhi!

I’m not too familiar with this topic, but I noticed this is a fairly old thread. I’d recommend creating a new post and linking this post to it, if you haven’t already. 
 

Newer posts reach a wider audience and tend to get more community engagement 🙂 happy to learn and dig into this topic a bit more with you and the community