Follow the video shown below to add a new array to the build part info sturct.

Next save your S_BuildPartInfo and go to the S_BuildingSave and follow the video below, you will change the Build Part Info variable to an array save then change it back to a variable again, this is done to recomplie the struct.

Next go to the BP_InventorySaveSystem and follow the video below once done compile the bp.

Next go to the BP_MasterBuildPart and delete the highlighted node shown in the image below.

Next follow the video below.

Add the highlighted shown in the image below.