I have an iMac and MacBook Pro and since I write about specialized topics, the computer is always changing my spelling. For example Plex was re-named to Alex and things like that so I was curious. Does iCloud automatically sync ‘learn spelling’ words to other computers on the same Apple ID?
The answer is no but someone on Stack Exchange asked and received a good answer.
The spellings are located in various files in ~/Library/Spelling. Namely, LocalDictionary and various localisation files such as en_GB. You can sync this entire folder using a sync method of your choice.
To sync via iCloud, symlink the folder to/from a folder in ~/Library/Mobile Documents. To sync via Dropbox, symlink the folder to/from a folder in your Dropbox.