I will just give you tips , it's a bit easy but we know that codewalker takes time to master of using it . .now you take note first that these object entities are placed in the World by a placement file called .ymap so they can be removed or transfer or be multiplied by editing their ymap files ..
by pressing letter T in codewalker there appear the toolbar ( now you can play and experiment how to use these tools therein).
now you can start editing( you can remove these objects by deleting their entries in its ymap file ) ., after all finishing edits save the ymap file you edited then you can put them in the custom_maps dlc mod. If it's not totally working , then makeup a backup of the original .ymap file then replace it with the one you edited.
for example :
hw1_01_long_0.ymap -- you can locate this file through search everywhere in search bar or by pressing the selection info window button(toolbar) then go to ymap at the very bottom and then click rpfFileEntry there you can see