Maka_CS

We're trying to connect Hotjar analytical service. It was done years ago, no longer worked, so I removed the tag from Google Tag Manager, tried to connect via Hotjar integration wizard, it worked but there was a verification error because the old tag is still present. What's the safest/quickest way to remove HTML tag from Squarespace? Should we enable developer mode and do it? Would we be able to disable it again to continue receiving template updates?