How to insert calc tab

I have a row of named tabs at the bottom of my Calc spreadsheet. I would like to add another but double-clicking no longer opens a sub menu offering that function.
How are tabs added to Calc ?
Thanks !

Rob

OS 10.14.6 / FireFox 72.0.2

Hello,

Try right mouse click on existing Tab and select Insert Sheet...

Dear Ratslinger, Double-clicking a Calc tab results in this menu: "Select All Sheets, Protect Sheet, View Gridlines, Sheet Events ".
I had reproduced the full menu when visiting a forgotten Release Notes link.
Does any of this sound familiar ?
I use a TrackPad for screen navigation.

Thanks !

Rob

Nope. Double clicking only gets me to rename a sheet. Right click gets me to list with Insert.