Rather than having to load hundreds of blockchains on Polkadot.
In a newly installed SubWallet
FirstCreate an Account or Import and Restore an Account, then the Network Selection screen will pop up. Search or scroll down to select the network(s) that you need to use, then hit Confirm. You will see all your selected networks when pressing the drop-down menu on the top. Apart from the four relay chains (Polkadot, Kusama, Westend Testnet & Rococo Testnet), all other networks are arranged in alphabetical order.
In an existing SubWallet
On the top drop-down menu, select Custom Networks. Search or scroll down to enable your desired networks, then press Done.
If you want to disconnect all networks, select Disconnect all. If you wish to revert to default (Polkadot Relay Chain and Kusama Relay Chain), click Reset to default.
If your networks aren't listed, hit Add Network to add your networks manually.