DealMaker is used to complete the forms and payment required to make an initial investment. Once a purchase is completed on DealMaker, the company will issue shares to the investor outside of DealMaker either with their law firm or a transfer agent (generally larger public companies use a transfer agent).
In order to transfer shares into a new name, the company and/or their transfer agent can assist you. Going forward to shares can also be stored in a brokerage account, in which case the broker can assist with the transfer of shares.
If you think that your heirs may need access to the original share purchase paperwork, you can share or store your password with them, along with your other passwords as you are doing for the rest of your estate planning.
Here is a link on how to reach the company for a purchase that was made using DealMaker.