How you are editing?
Do like this...
Left side give right click on triggers and click apply filter.
then give your trigger name. then it willl show your trigger, then copy the script. and paste it new tab and modify and click on F5.
Other wise click on Shift F4 after selecting trigger name. then it will show trigger script. then copy and paste it in new tab and modify and then click f5
Hope this will help you...
I'm trying to edit the trigger directly after opening it in a tab. Copy and paste had no effect but I did find that the problem went away after repeatedly closing and opening the trigger. I can't reproduce the problem now either!
Is your problem solved finally?
I can make the problem go away by filtering the triggers so that the only one I wish to edit is displayed. Minimising the sidebar also seems to help.