Hi, these are two different requests. Let's handle the missing entry under "In other languages" here. Confirming the problem.

For enabling importing, can you please file a separate request against "Wikimedia > Site requests", and link to a discussion page where it is shown that the Bengali Wiktionary community supports this change? For more information about how to request these kinds of changes, please see https://meta.wikimedia.org/wiki/Requesting_wiki_configuration_changes and feel free to forward that link to others who may want similar changes made in the future. Thanks!

The "In Other languages" section is a per wiki thing, maintenance on http://en.wiktionary.org/wiki/MediaWiki:Recentchangestext. You should ask a local admin to add bn:, but maybe there are rules, where bn: does not apply.

This needs to be fixed on-wiki by admins, nothing that needs code changes. Hence closing Bugzilla ticket as it's the wrong place here.