Yes. I assume SAMP Map editor is SAMP Map Construction ?
Follow the steps.
1) When you want to stop mapping, in the top corner there's a menu, press "Show Code", third from the left.
2) Select all the content and copy it. (Remember to scroll down.) (Right click > Copy )
3) Create a text document (If windows, right click on desktop New > Text document)
4) Open your newly created document, right click on it and > Paste.
Then when you want to continue mapping, Copy the content in the text document, and on SAMP editor press "Import paste" left of "show code".
Then all the objects should be in the map editor again and you can continue mapping.