I am not with Laminar Research; just a flight simmer not using steam but using an official version of X-Plane from the developers being Laminar Research.
I cannot answer your problem regarding transferring software from steam to your planned/proposed LR version purchase. If you do acquire a LR version it may be prudent to totally delete the Steam version to avoid any conflict. From what I have seen in this forum I understand that Steam installs the software differently to the LR version which installs to the desktop or a dedicated drive on your flight sim computer.
Steam is a 3rd party product whereby the steam creators are taking a commercial advantage of the development work carried out by Laminar Research (LR). Steam is not marketed by LR. It is a completely different product that will not mix with the LR version. I would suggest you acquire the official digital download version from LR as the many current PC builders, including Apple, no-longer include a DVD drive as part of their builds. If you want one you need to specifically order a unit or have it added by a third party after your purchase.
Steam version updates become available well after the LR version is released ie they are slow to react.
You most likely will not find anything in the LR knowledge base related to steam. You should also check the Steam forums for a solution to your problem.