Are there any tips and tricks regarding this search box ?
If I write text it, I think, only searches build #, and I know I can use prefix tag: to filter out tags, are there any other prefixes for branches, people, etc ?
There are no other prefixes. Currently it searches the build version field (build # column) in the database unless it is prefixed by tag: in which case it searches for matching build tags.
This does appear to be something we should look into improving - perhaps to allow searching the Started By, Branches and Status columns.