For all sorts of search,
Ctrl + F,
Ctrl + O and especially for search portals, adding the ability to use logical operators like and, or, not to combine search terms (like text, tags, references) will make search feature really powerful. E.g. create a search portal with rems that are tagged with both task and high priority.
Also, it would be cool if we can use something like parentheses () to control the precedence of these operators just like in typical logical expressions. E.g. task and (high priority or medium priority)