As a freelancer having exactly the same problem when working on multiple projects, I made Freeter (https://freeter.io). Give it a try - maybe it will be helpful to you.
I've been trying Freeter since it was posted here. It's definitely not bad, but I don't think it solves the isolation problem mentioned - but it does help me get my workspace back up after a restart.
I made this app because I constantly search for something and have to often re-type similar queries and setup same filters on search engines. Then I realized that it would be way better if I just could define scopes for specific searches, and quickly reuse them. Searchy does just that.