Let's say you have an existing channel named #channel and you want to move to #newchannel.
Use these commands on the libera.chat IRC network (may also work on other networks. I do not know) to forward users who join #channel to #newchannel:
/msg chanserv set #yourchannel mlock +if #yourotherchannel
/msg chanserv set #yourchannel guard on
NOTICE: You must not set any akick, or the kicked users would not be forwarded to your new channel.