Translation editor

Does the translation editor also accept {{t-needed}} as input?

No. Should it?

If we want to migrate away from the old templates, yes.

Meh. The markup added to the page is still {{t-needed|...}}. We may safely delete Template:trreq at this point (or redirect it to Template:t-needed), I think nothing uses it any more. "{{trreq}}" is just an arbitrary string. Though it may be confusing for some.