For example, on my calendar i have about 8 tickboxes in the Legend area, but usually only want to show 3 of them ticked.It's a pain t have to untick 5 of them every time i go to the calendar.

Miro in support has developed a fix for this, add this code to bottom of your page

<script>
setTimeout("jQuery('div#dmxAjaxCalendar1 > div.calendar_header > div.legend > table.legend > tbody > tr > td > div.event > div.text-outer > div.text > label > input').filter(function (index) {return index == 0|| index == 1|| index ==5 || index == 6|| index == 7|| index == 8;}).click()", 500);
</script>

Where the index numbers are zero based numbers of the checkboxes you wanted de-selected.
As i understand it, it basically fakes you clicking on each checkbox to deselect it.

Seems to work OK, but still might be a nice addition to include in the options for a future release.