Jitter offers minimal support for right-to-left languages at the moment. Letters can display in the right order and you can type text without issues. A couple of things aren't fully supported yet:
Editing bi-directional text: It displays correctly, but editing it directly in Jitter can be tricky. As a workaround, copy and paste your text from a different editor instead.
Ligatures spanning more than two characters: These aren't displayed correctly. This mostly affects Arabic, where letters won't always connect using the right ligatures. In the meantime, you can use a tool like this Arabic keyboard converter to fix your text before pasting it in. If you use a tool like this, make sure to force the text direction to left-to-right; these tools are typically built to work only in that setting.
We're working on improving support for right-to-left languages. Don't hesitate to reach out if you have feedback or questions!