The advertising data is stored in a buffer, and thus you should be able to modify/update it pretty easily when not advertising it (using the buffer that is). It should be something similar to just changing the data stored in the advertise data buffer.
Thanks for the answer! A representative of Cypress has confirmed it as well.
If the BLE module is not advertising, then I can modify the advertisement buffer directly (cyBle_discoveryModeInfo.advData->advData).
If the BLE module is advertising, then I need to wait for CYBLE_BLESS_STATE_EVENT_CLOSE state, modify the advertisement buffer (cyBle_discoveryModeInfo.advData->advData) and call CyBle_GapUpdateAdvData().
Exactly! Glad you got the answers you were looking for