There are only two options are available. 1. space and 2. comma.
If you want to set comma as delimiter for tag than go to
Admin > Posting and there find option
Use comma as the only tag separator and select it.
If you want to change the custom behaviour for this then look for the following file:
You have to modify two functions - qa_tag_click & qa_tag_typed_parts in that file.
Welcome to the Q&A site for Question2Answer.
If you have a question about Q2A, please ask in English.
To report a bug, please create a new issue on Github or ask a question here with the bug tag.
If you just want to try Q2A, please use the demo site.
May 7, 2020: Q2A 1.8.4 released!