I am using Adobe InDesign CC 2018 in Windows 10 64bit with Microsoft Office 365.
I have composed Tamil text in Microsoft Word. When I type or copy paste Tamil text from Microsoft Word or from a website, the text is not displaying correctly in Adobe InDesign.

It shows boxes highlighted in red. After changing the font to Anjal Inaimathi or any other Anjal tamil font, the text appear in Tamil but the characters are mixed such as modifiers or kombu and thunai kaal are not in place.

 

New and improved features for working in Tamil and other East Asian languages are available in the latest edition of Adobe InDesign CC.

Adobe World-Ready Composers

Adobe World-Ready composers enable you to create content in Tamil language. You can type in, and mix between, English, Tamil other Indian languages.

You can choose between available composers from the Paragraph panel menu (Windows > Paragraph > panel menu). For example, in InDesign, you can use the Adobe World-Ready Paragraph Composer. Or in Illustrator, you can use the Middle Eastern Single-line Composer.

Alternatively,  go to Edit > Preferences>Advanced Type> Select Adobe World-Ready Paragraph Composer and click close.

 

Please refer to the series of screenshots to enable Tamil text to render correctly.

Method1:

Method2: