Is it possible to merge columns headers in the report. (highlighted within red box in the attachment)
Our component doesn’t have such feature. But I can propose you an idea for the workaround. If you open DevTools you will see that each cell has several css classes. For example, an empty cell in the header has the following classes:
class="fm-cell fm-header fm-header-c fm-empty fm-ui-element“
If you override css for
fm-header-c fm-empty you can hide borders between cells and it will look like a merged cell.