Board Thread:Support Requests - Community Management/@comment-38359885-20200617072602/@comment-26611127-20200619170131

You aren't the creator of either wiki, so you can't request for one to be closed. Also, in order for a merge to take place, both communities must discuss and agree on the merge.

If one of the wiki's is inactive, then that could be a slightly different story. See Help:Merging communities.