Factorio Forums

Parameterized blueprints are difficult to edit because they cannot be placed without changes. For example, since value parameters are grouped by their value, if you have two formula-based values, if they evaluate to the same value upon placement these two distinct parameters get "merged". You also have to remember where your formula value parameters were because even if you give them distinct values like 999, 888 etc. they get evaluated on placement and what was formula or what wasn't is lost. You also can't really tell where a value was, if I have two constant combinators with a different formula parameter in them, I don't know which of the values is in which combinator.

Right now the best solution for editing parameterized BPs is keeping a "blueprint save" with the builds before they are turned into blueprints, loading it, making changes there, and using update blueprint on them, which kind of goes against the whole idea of blueprints.

I suggest a "raw" placement solution, which places a parameterized BP exactly as it stored in the blueprint, without running formulas

You kinda can do this, just with a few caveats:
Firstly, when placing the parametrised blueprint you wish to edit, don't select anything for the signal parameters. When you update the blueprint using "select new contents" any Formula that contains a raw parameter will be preserved.
Unfortunately the inverse is also true: any formula that does not contain a raw parameter is lost - including any formula that simply prompt for a number.

There is a workaround if you have at least 1 signal parameter - for every formula that doesn't already rely on a signal add then subtract p0_s from it.
Eg: say you prompt for an item and 3 numbers a, b & c and one formula only uses those numbers say "a * b + c", usually you would loose this formula when placing down the blueprint to edit it. But if instead you change it to "a * b + c + p0_s - p0_s" it can't calculate a result if you don't select anything for the item when you place it down and so the formula will be preserved.

Just note that the formula is stored in the blueprint, not the items placed in the world, which is why you don't get anything if you try using a new blueprint rather than updating the original (or a copy of it).