Hello @anon16282103,
it depends on the projects permissions.
If the projects are public within a public team then you can join it and make further changes if needed.
Now keep in mind there are different project permission settings so you might not be able to perform every action
For more info see:
For private projects it would require somebody from this project to add you in order for you to make changes.
Here is a tool provided by iDO that might help you a bit to get an overview on most projects: iDO Tools - Improve Asana with our tools and automations
And here is how you can get the list by using advanced search:
And here is a relevant feedback request that might be of interest: