Clicking on the ellipsis gives you more options:

Summary — change the issue summary,
Story points — add or change the story point estimation,
Status — set the status to eg. To Do, In Progress, Done, In Review,
Assignee — change the person assigned to the issue,
Priority — set a different priority for this issue,
Add child issue — create a new issue related to this one,
Open in Jira — open the issue page in Jira,
Copy — copy this element to the clipboard (you can use the shortcut CTRL/CMD + C),
Duplicate — create a duplicate on the board, next to the original element (achieve the same effect by pressing CTRL/CMD + D),
Cut — remove the element from the board and copy it to the clipboard at the same time (CTRL/CMD + X will trigger the same behavior),
Add new comment — add a note for your collaborators,
Lock — keep the element locked in place so it can’t be moved until it’s unlocked (also works with a shortcut CTRL/CMD + L),
Bring to front — move it to the front of other layers on the board (use CTRL/CMD + ] to do it from the keyboard),
Send to back — send it to the bottom of the layers on the board (use the shortcut CTRL/CMD + [ to do the same),
Remove — delete the element (you can also select the element and press DEL/backspace button on the keyboard),

Advanced:

Set sticky — when scrolling, the element will stay within the viewport so it’s always accessible from wherever you are on the board,
Disable shadow — remove the visual shadow underneath the element.

How to add and create Jira issues on a board?

Convert objects into new Jira issues — Step 1