I am using LibreOffice 5.0.2 (64-bit) on Windows 7 Prof. I have been a user of LO 3 onwards. Only recently started using Malayalam. I am unable the type the ZWJ (U+200D or 8205) and ZWNJ (U-200C or 8204) characters using the Windows’ built-in Malayalam keyboard. In Windows applications like Notepad the characters can be typed using the standards keys Ctrl+Shift+1 and Ctrl+Shift+3. But LO does not accept these keystrokes. Hence it creates problems in the chillu-letters in Malayalam.
(I have a workaround with macros which also has some font changing problems, since I am a newbie to LO-basic-macros. I will ask for clarifications on macros separately).