There is something similar all ready built into the editor.
First you click "Select Predefined Objects"
Then you highlight want you want to save and click "Add the Selection to the Objects" and name it. It will be in there for forever. You could also click the "New" button right next to the drop down menu and create your own object list. Afterwards you'll need to hit the disk icon to save it.
I don't really use it that often. I usually create a palette on the level somewhere or in a new level thats tabbed with the level I'm working on. Then whenever I need something I just highlight it and then copy and paste it where I need it.
Get creative!