Mandatory Field on Quotation

I’m trying to produce an exchange quotation (QU-75) and at the moment we have to put an outright price on the quotation.

If we are quoting the supply of an engine (for example) and taking in a core engine for a fixed price, we don’t necessarily want to add an outright price on every quotation as it won’t be relevant to the final invoice value.

Is it possible to make this field optional?