Policymaker, policy-maker, policy maker?

All pass my spell check in my browser, I imagine it’s personal preference.
I prefer Policy Maker myself.

protocol-creator

The concise Oxford English Dictionary prefers the one word sample,however variations are accepted and used frequently.

When what oasis is saying is the case, it usually indicates a phrase migrating to a single word. A recent example? Database, which started common usage a couple of decades ago as two words.

This is what a style guide is for in a publishing environment: to establish a preference among legitimate alternatives.

The main thing to remember in using one style rather than another is to keep it consistent within a document or set of documents. This extends to analogous words. For example, if you pluralize “index” as “indexes” (and not “indices”), you also have to use “appendixes” as the plural of “appendix” (and not “appendices”).

If I chose “policymaker,” I would then consider myself obligated to write “decisionmaker” if that term came up. I would prefer to hyphenate it for that reason. However, familiar compounds do tend to move from open (separate words) to hyphenated to solid (written as one word), and similar words can be at different stages in that process.