Pick the Environment\PropsSet folder inside a BakeMe folder you bake. The site opens the match prop sets already in it, as they are, and adds any of its that are missing. From then on, switching matches opens that match's file in the folder, and your edits save into it by themselves.
Where the folder can be
Chrome and Edge won't open anything inside system folders such as Program Files, Windows or AppData, which is where Steam puts the game and often the mod tools. They say the folder "contains system files", whatever it holds.
So keep a BakeMe folder of its own inside Desktop, Documents or Downloads (not those folders themselves), for example:
Documents\BakeMe_Propsets\Environment\PropsSet
Connect that PropsSet folder, then bake BakeMe_Propsets with your mod tool.
Nothing in the folder changes until you confirm on the next step.