Coinomi supports every ERC20 token. If the one you want to store isn't already on the "Add tokens - Ethereum" list in the app you can follow the instructions here to manually add the token wallet: https://coinomi.freshdesk.com/support/solutions/articles/29000009779-how-to-manually-add-an-erc20-token-
Using the wallet RPC on your view only (hot) wallet, you can call transfer with get_tx_metadata: true and do_not_relay: true which will yield an unsigned_txset in the response.
Then on the spend wallet RPC (your cold wallet), call sign_transfer, passing in the unsigned_txset from above, which will yield a signed_txset in the response.
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