So you've created an asynchronous proposal and now want to remove it from consideration.
You can go to your Tensions in the menu My proposal.
Click on the proposal you wish to remove. You will have the option to Remove Proposal.
Doing so will leave the proposal in your Tensions list as a drafted proposal so you can submit the proposal again at a later time or import it to the next meeting.
Note: If you choose to delete the proposal, it will be removed entirely.