Yes, if you work with multiple company entities in Teamleader Focus, you can set a default company entity.
To do this, follow these steps:
Go to Settings > Company information
Click on the three dots next to the company entity you'd like to set as default company entity
Click on Set as default
This will cause this company entity to be the default one, and therefore the one used by default when creating invoices, quotations or when using a signature when sending an email. Remember that even if this is marked as default, you can continue to manually select the other company entities when necessary.