i have a custom RE Component created in AEM 6.1 having category rte.coralui2 ( for my 5 custom plugins apart from OOB plugins ).
When I am migrating to 6.3 ( without any changes ) 5 custom plugins are not coming .
After following these following steps given in the suggestion also , its not working.
Rich Text Editor
If I am using rte.coralui3 , then only one plugin showing ( broken image ) but functionalities are not working.
Any pointer will help.
See this article to learn how to work with RTE on AEM 6.3 -- Configuring Experience Manager Rich Text Editor Plugins in a Touch UI Component Dialog