Odoo’s multi‑company logic is designed so each user has a default company and can manually switch or activate others. There isn’t a built‑in option to “auto‑activate all companies” at login, because Odoo enforces company boundaries for security and data segregation.

If you want a sales rep to always see opportunities across all branches without toggling, you have two main approaches:

• Access rights: Give the user access to all companies and configure their default company. They’ll still need to activate others if they want to work across them in the UI.

• Customization: Extend the login/session logic so all companies are activated automatically for that user. This usually means overriding the res.users context or writing a small module that sets allowed_company_ids at login.

by default Odoo requires manual activation for multi‑company users. To bypass that, you’d need a small customization that auto‑loads all allowed companies into the user’s session or creating such access rights that cover your need about this matter.