Unlike Office desktop applications, Power BI Desktop doesn’t keep track of more than one account at a time, which is quite annoying for people like myself who work across several tenants. Like many people I use a password manager, and until recently I had to copy and paste from Lastpass to the authentication modal box opened by Power BI Desktop.
Not anymore! Go to Options > Security > Authentication Browser > Use my default web browser. Now your authentication window is a regular browser tab which Lastpass (and I assume its competitors) will know how to fill in!
I’m not sure which version of Power BI Desktop introduced this, the “Learn More” link in the Options window just links to the Power BI documentation portal and I couldn’t find the actual page describing this functionality.
Bonus: this also works to switch tenants for dataflow sources.