Short answer. Yes. Separation of property may be total or partial, and it may cover present property, future property, or both. Where it is partial, the law supplies the answer for everything left out: property not agreed upon as separate pertains to the absolute community.
What the law says
Separation of property may refer to present or future property or both. It may be total or partial. In the latter case, the property not agreed upon as separate shall pertain to the absolute community.
Family Code, Article 144 — Separation May Be Total or Partial, Present or Future. Read the full provision →
Two axes, not one
The article gives a couple two independent choices, and it helps to see them separately. One is scope in time: the arrangement can reach present or future property or both, so you may separate what you own today while leaving what you later acquire to fall into the common pool, or the reverse. The other is extent: total or partial, meaning all of the property covered or only identified parts of it. A settlement can combine them — separating a named business and everything either spouse acquires from it, while leaving the rest untouched.
Silence has a default, and it is community
The last sentence is the one that decides real cases. Where the separation is partial, property not agreed upon as separate shall pertain to the absolute community. So an omission is not a gap to be argued about later; it is a decision, made by the law, in favour of the pool. That cuts against the way couples usually draft, which is to list what they mean to keep apart and leave everything else unmentioned on the assumption that unmentioned means untouched. Here, unmentioned means shared.
Describe what is separate, precisely
Because the default runs against separation, the drafting burden sits on the property you want kept apart. Identify it in a way that will still work in ten years: a lot by its title and technical description rather than by nickname; an account by institution and number; a business by its registration. Think, too, about what the property will turn into — proceeds of a sale, a replacement asset, shares issued on a reorganisation — because a description tied to a thing that no longer exists leaves its successor unmentioned, and therefore in the community.
Partial arrangements need a working inventory
A partial separation is only as good as the record that distinguishes the two categories in daily life. If separate funds are mixed into a joint account, or a separate lot is improved with common money, the categories blur and the default has room to operate. Keep the assets and their paperwork apart from the start, and keep an inventory you actually update. Bring that inventory, and the titles behind it, when you have the arrangement drawn or reviewed; it is what a lawyer works from.