Hello,
I don’t know if I could explain this clearly. When I write an Arabic word in edit panel and double-click on the middle glyphs that I want to edit, if that glyph is based on another glyph, it would open the original glyph beside it as expected (like when editing “khah-ar.medi” would open “hah-ar.medi”). But the problem is that the other glyph would changes to its initial form (in this example to “khah-ar.init”). And as you know the shape of that would be very different from its middle or end form that I’m working on. This was confusing at first that I didn’t know what was happening and now is annoying. It would be great that the shape of the glyph somehow stays on its original middle or final instance.
Also I guess that there is a bug in previewing of Tatweel (0640). The Arabic glyphs that come after It don’t convert to their middle or final forms at the preview band.