I found a way of extracting the Devanagari - QWERTY.keylayout from Apple's .bundle, and have been able to modify it with Ukelele to add several characters that are missing in it. Now I am able to enter: ऌ, ॠ, ॡ , कॢ and नॄ with these modifications. I have tried the Unicode signs for Svarita and Anudātta markings. However, the Anudātta marking overprints the signs like ू, ृ and ु, and I have not yet found a solution of how to get the Anudātta sign below these. Any suggestions?