u/A_Crawling_Bat

I have an idea for a hanging style colony pack (like hanging from a floating island) and I was wondering for ease of building : is there a way to have the builder place a block in particular or leave it as is ? I'd like to make it as user friendly as possible.

Here's an example : I make a hanging street/walkway that's held up by chains. Is there a way to make the builder place the chains up until they hit a block ?

I think I could use solid placeholders and have the builder use a specific block as filling (like a chain) but then you would have to change the fill type from one building to another depending on what the build uses.