Oh, I see what you mean. I'm afraid I don't know any way to do exactly what you ask. Now, what you want to do with this find may affect how you proceed. For example, if you want to do a replace, or even extract the found items, you could do it with one more step.
If you wanted to replace the string, you could put parens around the desired section, such as: "\[([^\[,]*),". In the replace string you could refer to the contents as "\1", which would be the string between the delimiters.
If you want to extract the contents into a list, you can check "List Lines Containing String" in the find dialog and paste them into a file. It would then be a simple step to get rid of the delimiters. (Replace "\[([^\[,]*)," with "\1")
I'm not sure how else to approach it. Maybe if you could give some more detail on what you want to do once you have found the string, I'd have some other ideas.