In Bengali Phonetic (ITRANS) keyboard there is no way to type nairṛti (नैरृति) in Bengali (নৈর্ঋতি).
In Bengali Phonetic (ITRANS) keyboard developed by Shree Devi Kumar (link), there is no way to type nairṛti (नैरृति) in Bengali (নৈর্ঋতি). To be specific, you cannot type rṛ (रृ) in Bengali (র্ঋ), which is a problem because some Sanskrit words do have such letter. If you want to type with this keyboard, it becomes like this nairṛti (নৈরৃতি), which is wrong. It should be nairṛti(নৈর্ঋতি). But, there is no way to write it with this keyboard. Somehow you have to find a way to place a Bengali 'ref' over the ṛ(ঋ), like this র্ঋ. I wrote this র্ঋ here using a different keyboard.
@Shreeshrii is this something you would like to add support for? I looked at the source and it looks like the usual way of producing virama produces something else for this sequence. R^ produces U+09E0.
Try adding a virāma between the র and the ঋ. That works in Gautami Bangla/Bengali. I suspect it will work here as well.