Second Brain in Excel: A Simple Notes and Project Template

You can build a second brain in Excel with four linked sheets: Notes, Sources, Projects, and Review. Keep one record per row, use stable IDs to connect records, and write a short context summary before asking an AI to use the information.

The same basic layout works in Google Sheets. When keeping tasks, decisions, and checkpoints synchronized becomes cumbersome, fenbs can hold that shared work record while the workbook remains your index of useful knowledge.

Which sheets do you need to start?

Start with a workbook for one area of work, such as a freelance design practice. The following structure is a suggested template you build yourself. Keep full documents in their existing homes and use the workbook to explain why they matter.

Use plain dates such as October 20, 2026 in explanatory examples and real date values in date columns. Choose one date convention for the workbook. A copied date that becomes ordinary text can stop sorting as you expect.

Keep state labels few and clear: Draft, Checked, Needs review, and Archived are enough for notes. These describe the reliability of your reference records. They are separate from the progress of an active task.

For the purpose behind the collection, read what an AI second brain is. This template focuses on a spreadsheet you can maintain, rather than choosing a complete knowledge app.

What does a filled-in example look like?

Say you are preparing a studio website. You have an approved service list, a note about writing clear service descriptions, and a draft that needs checking. The IDs let you connect those records without rewriting the same source title everywhere.

NOTES
Note ID | Title | Summary | Source ID | Project ID | State
N-001 | Service claim wording | Use only services named in the approved list | S-001 | P-001 | Checked
N-002 | Client example | Permission to publish still needs confirmation | S-002 | P-001 | Needs review

SOURCES
Source ID | Title | URL | Scope
S-001 | Approved service list | [document link] | Website service claims
S-002 | Client example draft | [document link] | Draft only; no publication approval

PROJECTS
Project ID | Goal | Next action | Open question
P-001 | Prepare homepage for review | Check claims against S-001 | Can we publish the client example?

REVIEW
Record ID | Reason | Reviewer | Result
N-002 | Confirm publication permission | Studio owner | Waiting for answer

Assign an ID when you add a record and keep it unchanged. Avoid using the row number as the ID: sorting and inserting rows should not change what a reference means. If a note becomes irrelevant, archive it rather than reusing its ID for a different idea.

When one note supports several projects, add a small linking sheet with Note ID and Project ID columns. Each row then records one connection. A comma-separated list is tolerable at first, but becomes difficult to filter consistently as the workbook grows.

How do you make the workbook easy to navigate?

In Excel, turn each data range into a table with headers; Microsoft explains the table setup↗ (opens in a new tab). Use descriptive column names and keep one header row. Do not scatter unrelated mini-tables through the middle of your records.

In Google Sheets, use the documented filtering options↗ (opens in a new tab) to narrow a sheet to the project or review state you need. Filter the whole data range together. Sorting one isolated column can separate an idea from its source and make the workbook misleading.

Store the full source URL in its own column even when you show a friendly link label elsewhere. Google documents the HYPERLINK function↗ (opens in a new tab) for making a labeled link. A readable label helps navigation, while the plain URL keeps the destination easy to inspect and copy.

Before building more formulas, try finding every checked note for your active project. Then try finding every source that needs review. If those ordinary questions are difficult, repair the columns before designing a complicated overview.

What should you give an AI from the spreadsheet?

Prepare a small context packet for the specific task. Include the project goal, the relevant checked notes, their source references, and the unresolved questions. A workbook full of mixed topics gives an assistant more opportunities to use the wrong material.

Task: Review the homepage service claims.
Project: P-001, prepare a draft for human review.
Use: N-001 and the approved service list S-001.
Unresolved: N-002 does not establish publication permission.
Output: A list of claims, their supporting source, and missing evidence.
Do not treat a draft or an open question as approval.
If the original document is unavailable, say what you cannot check.

Do not assume an assistant can read a workbook merely because you named it in chat. Copy the selected rows, provide an approved export, or use a connection documented by your AI app. Check what it actually received before relying on its answer.

An assistant also needs to understand which records describe old work. The AI brain guide explains the value of keeping reusable context outside a chat. In this workbook, checked dates and review notes supply the boundaries around that context.

For changing project state, fenbs gives supported assistants a common place to read Rules, current work, and Where we left off. That reduces the need to assemble a fresh status summary from spreadsheet rows each time.

How do you review notes without reviewing everything?

Review records because something gives you a reason to doubt or reuse them. A source changed, a project restarted, or a colleague challenged a summary. Add that reason to the Review sheet so the person checking it knows what to investigate.

1. Open the original source and confirm it still supports the note.
2. Check whether the note applies to the current project and audience.
3. Correct the summary or mark it Needs review if evidence is missing.
4. Record the check date, result, and next action without erasing useful history.

Test the system with one deliberate error, such as a note pointing to the wrong source ID. Can you find and repair it? A neat workbook is only useful when its links survive ordinary editing and its uncertainty stays visible.

How to do this with fenbs

1. Create a free account. It is free for one person, with no credit card, so you can test one project before changing your wider setup.
2. Add the project and its active tasks. Write the current goal and next step in plain words rather than copying the entire workbook.
3. Record the decisions people have approved, keep unresolved choices open, and add useful source references to Links and listings or AI context notes.
4. Connect a supported assistant from Integrations, ask it to read the project context, and have it save progress before the session ends.

fenbs is not the right fit if your main need is spreadsheet calculations or a personal reference index that you already maintain comfortably. Keep those jobs in the workbook. Use fenbs when tasks, decisions, and handoffs need a shared record.

For a repository-based approach, see the separate GitHub second brain guide. The second brain topic covers other setups. The smallest useful spreadsheet is the one you can explain, check, and keep current.