When I have to enter the English translation, some verbs expect a "to" in front, others don't allow it. That's very annoying.
I see three ways to fix that: Add a synonym without "to" for all of them. I'd do that myself, but I see no way to add a translation. Change the code of memrise itself, so the "to"s become optional for all of them. * Introduce some syntax denoting optional parts, and use that syntax on all verbs. Something like "to paint". Also requires some changes to memrise itself, but is more general, and can be used in other contexts too. So this would be my preferred solution.