If the form is 100% identical you can copy the yui for that block and paste it to a new page by using a code block.
Note: you won't be able to tweak that 2nd form without adding code to the code block. Also, if you ever delete the 'master form', the copied versions will over time be removed by Squarespace.
Maybe not the best way, but it works.
Another option: https://www.kathomalley.com/blog-original/2016/9/19/want-to-duplicate-or-copy-the-form-block-in-squarespace-try-this
Would be nice if Squarespace would allow us to copy forms...