there is no filtering by regular expressions in the current V2 beta releases. This has been droped in favor of the new functions that can be used in the complex filter tab.
Do you use a search expression that can not be represented by using the complex filter?
We will evaluate your suggestion to re-add the regex/wildcards filters in addition to the new filter functions, thank you for your feedback.
At the moment there is no in depth documention for the complex filter functions planed, as we thought they are self-explanatory. Are there any obscurities we should document?