The maximum size for a cross-functional team is 8-12. As it is only the avatars of six users are shown immediately, the rest are hidden under the "+" icon. This is quite annoying for the team as it means extra clicking, but there is also a feeling that Jira is treating some team members differently. In other words, not a good user experience.

My suggestion is to allow up to 12 avatars be shown be default at the top of the Kanban board before employing the "+" icon. There is plenty of space there. Alternatively, make the number of avatars shown configurable.

Copied from closed duplicate JSWCLOUD-20991 – As a Board Admin, I'd like to customize the number of users appearing on the Assignee Filter on a SW board:
When accessing a Kanban or a Scrum board, you can click on users' avatar to apply an Assignee Filter and displaying only cards assigned to that user.

As a Board Admin, I'd like to customize the number of avatars that will appear there, to reduce or increase that number which currently it's only 6 users.

You can click on +"number" to display a drop-down menu to show all the users but it would be nice to have this customization.