I don't want a lot of sticky parameters, just a few to filter out the large percentage of junk that clutters my search results.
Intentionally searching for parts with lead or inactive parts would be less than 1% of my searches.
My searches should not have state. I wouldn't want a sticky manufacturer name. I agree that this would cause confusion.
My account should have a state, which is that I am interested in active, lead-free parts.
Some customers would want other states, for example some only want to see automotive-grade or industrial-grade parts. This would be difficult to implement, because there is no cross-category button for that now. However, it looks like there is a button for mil-spec parts. Being able to have this always pressed would make sense at the account level, at least for those who have to work with that eclectic Americana.
I can't emphasize enough how important it is to put this configuration in the URL of every search.
There would also be confusion if I mailed a URL to myself when I was logged in, and got different results from it while I was logged out. The benefit of being logged in should not ruin the glorious URLs of parts.io!
The trick will be to make the user configuration easy enough to use such that users would not log out in order to turn off their own filters.
Another way to implement this is to give users their own list of named partially-filled-out searches.
For example, I normally only ever use X7R or C0G ceramic capacitors from Tier 1 suppliers. There is also a maximum size that I use. However, this is a more advanced capability and it would get little usage. Only a small percentage of users would even try it, and most of the ones that did probably wouldn't like it. It would be great for power-users. For this feature, giving the searches a name would help reduce the confusion. A big title could say "Custom Search: tomacorp Custom Ceramic Capacitor Search Results" and have a nearby button to go back to the full search.