ads.tiktok.com → Tools → Events.Field: TikTok Pixel ID.
ads.snapchat.com → Ads manager → Events.Field: Snap Pixel ID.
linkedin.com/campaignmanager.Field: LinkedIn Partner ID.
If you need a tag that is not in the list, paste its code into Custom head code or Custom body code on the same page.
Careful: anything you paste there runs on every page. Only paste code from a source you trust.