I havent used synEdit for a while, but today I found that I needed a good editor for a form with script support. As I went to download synEdit (which my mind had frozen in time
I strongly recommend the use of Scintilla. It has all features you are looking for. It is much more capable and mature than SynEdit. The development of SynEdit decreased in the last yeast to almost standstill. The only problem of Scintilla is that the no one is updating the Delphi code that binds to it. The SourceForge project is not active anymore. You can find Delphi code in the following URLs:
Borland Delphi control wrapper for Scintilla and Delphi Components
The latter contains the most recent code. It is not difficult to update it to add recent features of Scintilla.