You have a few options available to you within PEXA.
You can create a workspace as Incoming Proprietor, with the settlement date and time entered, and then create a priority notice. You can lodge the priority notice and then use the same workspace to create and process the transfer transaction. For more details around a priority notice, please refer to this article.
Alternatively, if you wish to lodge a purchasers caveat, probably the simplest way is to create a lodge the caveat in it's own workspace. The transfer transaction would then be in a separate workspace.
If anyone has any further experience around this scenario, please feel free to add some additional commentary.
@JHLegal, please let us know if you require any further assistance and be sure to update us as to how you go.