Problem Definition

I initiated import of about 20-30 accounts from Metamask in one go (after using the workaround in #8334), with the option to scan multiple EVM chains enabled. Then it just stuck on the modal dialog for adding accounts for a long time (10s of minutes probably), with the spinner going around, and a cancel button as the only obviously available user account. I'm guessing that ~25 accounts multiplied by several EVM chains led to the need for hundreds of API calls.

As I was writing this description, the modal dialog closed by itself, hence the lack of screenshots and slightly fuzzy description above. Now I can use Rotki as normal while the scanning continues in the background, so all is well; but I think the import process needs to account for the possibility that it will take a long time, and immediately start in the background by default rather than making the user choose between waiting indefinitely and clicking the cancel button.

Note: Also happen when many addresses are being added manually.