I can’t find this mentioned anywhere but, unless I'm completely puddled, the TABCLOSEALL=left and TABCLOSEALL=right commands work the wrong way round.
If I open three tabs and select the central one, then running TABCLOSEALL=left from a command window closes the right hand tab, and TABCLOSEALL=right closes the left hand tab.
The manual clearly states the opposite: “TABCLOSEALL/O: Closes all Folder Tabs except the current one. If you specify TABCLOSEALL=left then only tabs to the left of the current tab are closed - likewise for TABCLOSEALL=right”.
FWIW I tested it with this button that I use to toggle a command window (as suggested in one of the DOpus tutorials):
<?xml version="1.0"?> Toggle Cmd window toolbar Toggle Cmd window toolbar #newtoolbar Toolbar NAME="Command box" TOGGLE STATE=bottom