It can be done through the export / import function under the file menu. 

Can't remember the exact steps, but always wise to back up everything before you attempt.

I recall that you have to select the listings you wish to swap and then select export items, and follow the prompts that will save them to a file in turbo lister format CSV format ??. 

Then log into the user ID you wish to put them in, and under inventory create a folder to import them into and select import items from file etc etc.

Or something like that .....