Looking for mentions of karma related to actions taken while dreaming
I think it's listed as a point of controversy in the Abhidhamma -- Kv 22.6:

Controverted Point: That all dream-consciousness is ethically neutral.
22.6.1 Theravādin: You admit, do you not, that a dreamer may (in dreams) commit murder, theft, etc.? How then can you call such consciousness ethically neutral?
22.6.2 Uttarapāthakas: If I am wrong, was it not said by the Exalted One that dream-consciousness was negligible? If so, my proposition holds good.

I think the (Theravādin) argument is that intention (e.g. intention to murder) may be present, therefore it's not ethically neutral.
I think the counter-argument is that there's no material result, so if it's not neutral it's negligible.
See also the Vinaya -- that defines offences (e.g. killing) in some detail or legalistically (i.e. in more detail than the suttas do) -- and there, there are various (several) conditions which must be met for the offence of e.g. &quot;killing&quot; to have occurred, one of which is that somebody has to die -- and in a dream, nobody is really killed, so that wouldn't be counted (and punished) as the offence of killing.
The Abhidhamma is considered part of the Pali canon, even if it isn't all quotes from the Buddha.
In Tsongkhapa's Praise for Dependent Relativity it is mentioned that the karma of killing in a dream was a question answered by the Buddha, but no sources are provided.
So far as I known, the commentary to the Vinaya pronounces the non-punishment of sexual actions performed while dreaming (while also saying it's better not to).
It's not exacty right to equate the working of kamma with the rules of the Vinaya, however that may be the best we have -- because the Vinaya is defined in detail whereas the suttas don't describe kamma in every detail -- even say that the precise workings of kamma is known to the Buddha but is unconjecturable -- and, the Vinaya was defined by the Buddha.