as far as I know, the only ways to change the order would be to start a new version of your project, or download a copy of your project to your hard drive, unzip the whole project, open the project.c3proj file in a text editor.
near the beginning is a section called ObjectTypes, I haven't tried this with C3 (only tried in C2), but if you rearrange the items into the order you want to pin in, then it should eliminate the lag.
make sure you don't break the code - each item has a comma after it except the last item, so watch out for that.
then save the file, re-zip the whole thing, and open in C3 and test.
this seems like a poor way to deal with this problem though, and if it isn't documented anywhere there is no guaranty that a future update wont change how this works.
pinning everything to the same base object seems easier to me, and more likely to continue working in the future. Plus, if you have overlapping panels (as I often do) then knowing all the objects that belong to a panel makes it easier to pick the objects to move a panel to the front, or send it to the back, or close it.
EDIT: just tried rearranging the ObjectTypes section in Dop's sample file, and it does fix the lag.