PB 188.8.131.52 on Windows XP
Pressing Tab, Enter has no effect in 5.5, but pressing Enter does. So all you have to do if you want to invoke Extended Search is to press Enter (after adding appropriate wildcards).
I seem to recall that pressing Enter like this also worked in 5.0, though I may be wrong. I can't recall ever finding it was necessary to press Tab beforehand.
Quote: This made for a very quick transition from instant search to advanced search (e.g. TAB - ENTER), leaving one's hands on the keyboard.
Quote: Performing an Extended Search (p135, 5.0 User Guide)
To perform an extended search: Type what you’re looking for in the Search field, then click the Search button Your Search results will appear in the Search tab.
What you were getting was not Advanced Search at all, but Extended Search, which is Advanced Search with all the stops pulled out. Sure, more convenient to hit Enter than pressing F9, but less useful since my results got overloaded with false positives, including matching terms found in Thought labels, attachments, etc. If that's what you want, fine. But unless you designed your Brain to take advantage of Extended Search by deliberately avoiding using attachments, including text files, and deliberately leaving Thought labels blank, any extraneous material in there that matches will be included in Extended Search results.
On top of this, you have to be so careful when going from Instant to Extended Search to remember to add wildcards. For example, if I have Thoughts named object 1, ... object 4, all these are instantly findable in Instant Search if I type ob, but if I press Enter I get "No results found". That is, not until I add the asterisk wildcard, making the search term ob*. Even then it's not 100% reliable, IMO not entirely due to the vagaries of word expansion.
However, I'd welcome it if they changed the design so that pressing Enter while in the Search Edit Field couldn't invoke Extended Search, but obliged one to press the Tab key first. The two search engines are so different in their requirements, it's best to make a clear distinction between them. One of my first truly baffling experiences with PB was working out why clicking Search always produced "No results found". Until I studied the manual closely, this seemed to be completely counterintuitive.