custom body code

hello - so im trying to add a body code to all over the website (tag manager code) and the only option from settings is into the head but into the body code so i looked online and saw there is a way to make the element as a symbol but still i need to go page by page and to paste it in every page…we have over 100 pages and im looking for a way to paste this body code all over the website page.
any idea?

Webflow does not have a template engine for pages so the only easy step is if you used a component on all pages. You could then update the component with an embed. If not manual is the only way. If you have to do the latter you might want to replace your header with a component for future simplicity of updates.