Startup Pins v1.0
I disliked the pinned tab behavior, so I created this extension to overwrite the behavior to my liking.
Do note that this extension overrides default pinned tab behavior.
Usage:
go to "about:addons".
Click on the "Startup Pins" addon.
Go to the "preferences" tab.
Add the urls you want pinned at startup.
Known issues:
"about:" tabs do not work with this extension.
These can be pinned in the regular way and the extension will not override this behaviour.