I am not an electrician.
If I understand your question, you are considering providing electricity to a shed near your RV by connecting to the AC electrical supply in your trailer. There are two issues with this that as a layman I'm concerned about:
1) If your trailer has a 30 amp supply - that's barely enough to power the trailer, without also having to power whatever equipment you might need to use in the shed.
2) Grounding: the neutral and the ground in a trailer are not bonded together; the neutral and the ground in a building are supposed to be bonded together. But you could not bond the supply in the shed without also effectively bonding the system in the trailer, which would not be a good idea.
Electricians may have a much better answer for you and hopefully one will reply.
There's lots of advice and information in forums... sometimes it is correct. For example, all of my posts are made by a political appointee who got the job as a reward for contributions to my diesel bill.
2011 Jayco 28.5RLS; 2008 Chevy Duramax; Pullrite Superglide Hitch