A storefront admin, a supplier portal and a marketplace seller account are three different jobs with three different logins, and they end up in the same browser because that is where the browser is. The first time a marketplace shows you a session you did not expect, the reason is usually that all three shared one cookie jar.
Split the back offices
One profile per storefront, per supplier portal and per marketplace account. Nothing crosses between them because nothing is shared in the first place: separate directories, separate stored sessions, separate device identities.
Verify the route before an account sits behind it
Add your proxies to the library and test them. The test reports the outbound address it actually observed, which is not always the country the provider listed, and it names the way a test failed rather than showing a red dot. Assigning an endpoint copies it onto the profile, so no two profiles share a live credential.
Organise for a catalogue's worth of accounts
- Folders per region or per client, groups per job
- Notes and tags on the row, matched by the same search field as the name
- Bulk import that shows you what it parsed before it writes anything
- Bulk moves with an undo, because reorganising forty rows should not be forty decisions