This is not currently supported by MF Connect.

Jira UI modification/enhancement via Jira add-on is out of scope for Connect - Connect is focused on background sync.
However, it is unclear to me if for what you describe, a Jira add-on would be required, in the first place.

In addition, formatting AccuRev data specifically for Jira is unusual for Connect.
Connect tries to be a endpoint-agnostic as possible - the Jira connector only does Jira things, the AccuRev connector only does AccuRev things.

That said, depending on details (I am not that familiar with the AccuSync tool), some of this is likely possible by just enhancing the AccuRev connector, and in a fashion that is not dependent on Jira.

However, no such enhancement is currently planned, and it would rank below a number of more high-profile enhancements already on the backlog.
If you are interested in such an ER, please use the Idea Exchange capability of this community.
Take care to describe the idea/enhancement in a way so that other customers can easily understand it and potentially vote for it.
If you can include an AccuSync example, it would likely help with this, as well.

First of all, why you claimed "I am not that familiar with the AccuSync tool". AccuSync is OpenText product, no matter it inherited from other company or not, I hope you talk with somebody before you answer the question! Because your company owns AccuSync, I didn't include the screenshot, you can find out what it looks on your own! Furthermore, I described it looks like a table with nice format, instead of plain json. Jira activity tab would format this multi line text field. I opened this discussion because your OpenText support member suggested me to do this, when we were prototyping MFConnect with Jira Cloud and AccuRev. Are we going to an infinite circle? Can you talk with Jonathan Valverde, the support person?

First of all, why you claimed "I am not that familiar with the AccuSync tool". AccuSync is OpenText product, no matter it inherited from other company or not, I hope you talk with somebody before you answer the question! Because your company owns AccuSync, I didn't include the screenshot, you can find out what it looks on your own! Furthermore, I described it looks like a table with nice format, instead of plain json. Jira activity tab would format this multi line text field. I opened this discussion because your OpenText support member suggested me to do this, when we were prototyping MFConnect with Jira Cloud and AccuRev. Are we going to an infinite circle? Can you talk with Jonathan Valverde, the support person?

First of all, you might want to note that I wrote "not that familiar". I did not write that I do not know AccuRev/AccuWork/AccuSync, at all.

Second, just because AccuSync provides a capability in one specific technical manner, this does not mean that Connect should or would or could provide it in exactly the same manner. What counts is the value you derive from it - not the specific implementation path chosen.

Third, Jonathan from the Connect product support team provided you with correct guidance. Connect currently does not offer what you asked for, thus this is an enhancement request.
The preferred way to general submit enhancement requests that can be of value to other customers, as well, is Idea Exchange here in this community.

Fourth, authoring such Idea Exchange ERs is in the domain of the requestor/customer/submitter.
One purpose of IDEx is specifically to include customer-to-customer collaboration on top of standard customer-vendor communication.