I think so. Edit the community on the Lemmy side and add the account there, it's not something you can do from PieFed as the community is on a Lemmy instance.
post
Mlem has an add moderator button under the community moderation tab. I just added my piefed account as a mod on one of my lemmy communities.
I also was able to appoint a piefed account from the web interface. From a part or comment there is a hamburger menu and at the very bottom is an appoint moderator option.

replies:
all 4 comments