IMPORTANT NOTE: Please be aware that running the "Re-Deploy" option under OneClick web page > Administration > Report Manager > Jaspersoft Integration page will OVERWRITE changes made to Domains. If you are making the above changes to add Global Collections to Domains, then you want to back up Jaspersoft data in case "Re-Deploy" is run. You would then have to re-import your Jaspersoft backup and Domain edits.
Please reference knowledge article 95735 "How-To Backup Custom Jaspersoft Adhoc Reports" for more information regarding Jaspersoft content Export/Import procedure.
For newer versions of Jaspersoft:
If you go into View > Repository up top and then go to Public > ca > Spectrum > domains you can select > right-click> edit on the GC object from there and it should bring you into the editor.