Online Giving Form:

Currently, we can only pass in appeal, campaign, designation, and designation name in the url that will then populate the form hidden fields.

https://webfiles-sc1.blackbaud.com/files/support/helpfiles/tcs/content/donfm-param-form-webpages.html

We want the ability to add another custom url parameter that passes into a custom attribute on the gift. This would be a hidden field just like the desid and appealid.