In Rally, I am wanting to pre-populate a custom field on a new defect using the URL. For example if . a user navigated to https://rally1.rallydev.com/#/XXXXXXXXXX/detail/defect/new?c_MyCustomField=33 they would see the MyCustomField field populated with the value 33. Is there an easy way to get this done using the URL?
Unfortunately I don't know of a way to do this. I would recommend that you post it as a suggestion to our Idea Manager community at https://ideas.rallydev.com so that other users can add their votes and comments to it. This could help it gain additional support and attention. I'm sorry that I don't have a more helpful answer to offer.
Do you have some more details on what you're trying to accomplish? There are a couple options:
Just let me know if you have questions on either of these.