best tip i can give in make a basic map to use see item with a red-x on it, then save it nameless.bms and nameless.mis (map type death match or coop host it as lan), this way you go in to see item on the map.
2nd reopen map editor the main map you working on mis map on the 2nd page nameless.mis then locate the item and copy past it on the main map mis/ bms you like to make for all to use
then after you see what item you like to use that has the red-x to then
its been a super long time i did it, but that's was my favorite way to see items with red-x in the map editor image of them.
btw set spawn point some were outside the area were you have item at, then it be faster to get them. don't stack them on top of each other
to see the nameless.bms item start the game and host it lan get a closer look at them items with red-x
page one inside the map editor use for maps you working on and page 2 use for copy and past item from to page 1 ether page for mis map type
this all so a great way to test a map! see how everything going into place/ location on the map too
wire frame is a great tool to use! lining item with or stack them like flame on a smoke stack