I first made a database with demo data, and there I filled the form for the company. From Companies / (check on company) / Action / Export I managed to export a .csv with the company data (phone, address, etc).
Then I made a new database without demo data, and tried importing the .csv exported previously. When I then go to Settings / Companies / Import, the problem is this:
... that is - I click on Browse, choose the .csv - but after that, Validate is still greyed out and cannot be pressed, and the refresh button seems not to be doing anything either.
What am I doing wrong, and how can I export company data as .csv from Odoo, such that I can re-import that data in Odoo for a different database?
Unfortunately I cannot edit the OP question (403 forbidden) so I'll add here: all this happens with the default admin user, so probably it is not due to misconfiguration of user permissions (I hope?!)