Okteta and the framework Kasten is designed in a very modular way, with a lot of interfaces. So it should be easily extendable. While there isn't yet a real plugin system, new plugins/modules can be simply added directly in the code for now.
Find below a list of places where Okteta can be extended:
Okteta::AbstractByteArrayModel - not yet documented
Okteta::CharCodec/Okteta::ValueCodec - not yet documented
Binary Filter - see kasten/controllers/view/libbytearrayfilter/README_developers.md
_Checksum/Hashsum - see kasten/controllers/view/libbytearraychecksum/README_developers.md
Encoder (for Export) - not yet documented
Kasten::AbstractModel/Kasten::AbstractDocument/Kasten::AbstractSynchronizer - not yet documented
Kasten::AbstractView - not yet documented
Kasten::AbstractXmlGuiController - not yet documented
Kasten::AbstractTool/Kasten::AbstractTool(Inline)View - not yet documented
and some more...