Can the gadgets-definition-edit and gadgets-edit permissions be added to the stewards and interface administrators groups for WMF projects? While this isn't really live yet, edge cases have arisen that currently require contacting WMF staff (the only group with this access) to make adjustments.
See example: https://en.wikipedia.org/w/index.php?title=Wikipedia:Administrators%27_noticeboard&oldid=909187898#Add_maintenance_template from enwiki