For example to reproduce create dimension in action scope using below regex:

[{"dimension":"url","pattern":"/abcdefghijkl(*)/"}]

See https://3v4l.org/8ENBl trigggers a warning in the logs:

PHP Warning: preg_match(): Compilation failed: nothing to repeat at offset 15 in plugins/CustomDimensions/Dimension/Extraction.php on line 117

Ideally, in all plugins where it is possible to define a regex, we validate that the regex is at "valid". For example Goals etc. This will increase the correctness of the tracked data.

If the regex is not valid, then an error should be shown.