As a QASH holder, you don't need to take any action regarding the rebrand.
In the initial phase, the ERC-20 smart contract address will be the same, as are the token supply, decimals and other specifics. All that will happen is the token name being changed from QASH to Liquid and the ticker from $QASH to the new ticker (to be confirmed). The contract will reflect these changes.
The token swap will come later with the full launch of the LDL.