Possible to add a network to MEW web v6?

I think in older version (perhaps v4 or v5) you could add a network by filling in the chain_id, rpc_url and explorer_url, or something like that. Is that still possible? Maybe by messing with the currentNetwork object in the settings backup / restore?

Is the only option to run a MEW web server locally?

PS… I'm trying to add Mumbai BTW

Possible to add a network to MEW web v6?