Welcome to the OptoForums! You're right, that's not a built-in command. In PACs/Ultimate I/O you have a few options (any chance you'll be upgrading soon)?
In both PAC Control and OptoControl you can write your own command to do this (a subroutine, check out this post on subs).
However, if you use an for loop in OptoScript (the yellow hexagonal block), it's just a few lines of code like this:
// loop through table index values 0 through 9 and move value in stTableFrom to stTableTo
for nTableIndex = 0 to 9 step 1
stTableTo[nTableIndex] = stTableFrom[nTableIndex];
Or if you want to get a little fancier, especially if the lengths of those tables might change or might be different from each other, you can add some sanity checking before the loop like this:
// Get the lengths of my 2 string tables
nTableLength1 = GetLengthOfTable( stTable1 );
nTableLength2 = GetLengthOfTable( stTable2 );
// Figure out which one is smaller, so I don't run off the end
nStringsToCopy = Min( nTableLength1, nTableLength2 );
// Loop through each index until we run out of them and copy from Table1 to Table2
for nTableIndex = 0 to (nStringsToCopy - 1) step 1
stTable2[nTableIndex] = stTable1[nTableIndex];
I know OptoScript isn't for everyone, but when it comes to strings and loops especially, it can save you some time!