Can I use an asset attached to a UTXO in other types of Counterparty transactions?

No. Counterparty assets that are in UTXOs can only be be moved from one UTXO to another; you cannot, for example, place an order on the DEX or open a dispenser for a UTXO-attached asset. If you want to use a UTXO-attached asset in a Counterparty transaction you must first detach it from a UTXO. This can be done either as part of the Horizon Market swap purchasing process or through Horizon Wallet by simply selecting the following button.

Note that if an asset balance is detached for which there is a corresponding open listing on Horizon market, the listing will be automatically delisted.