Currently, if you try to disable tab grouping by emptying Title grouping regex or Path grouping regex it doesn’t work – empty regex is interpreted as “use default settings”. It is safe, but counterintuitive and for the next Tabs Studio version I’ve changed empty regex to mean “disable tab grouping”. If you want to disable tab grouping in the current version – write something non-capturing like “don’t group” as a regex.
If you enter invalid regex (e.g. “?” that shows the error parsing “?” – Quantifier {x,y} following nothing) and save it, then, again, default settings are used for tab grouping. I think safety of default settings is still valuable here.
Tabs Studio Blog (organizing Visual Studio document tabs) 