In version 6 of full calendar there is a possibility to inject a content via ng-template. Example is based on eventContent.
<full-calendar [options]="calendarOptions">
<ng-template #eventContent let-arg>
<b>{{ arg.event.title }}</b>
</ng-template>
</full-calendar>
Is it also possible for a header? I couldn't find an information about it. I tried with #header and #headerToolbar but it's not really working.