Dear Zarique,

I am not entirely sure what you mean with "multiple screening for level 1.", but I guess the answer to your question depends on how you have marked the studies so far. The aim of the exercise is to assign all "to be re-screened" papers to one administrative (allocation) code. With this done, allocating the appropriate studies to your collaborator will be straight-forward.

You can create the allocation code in any code-set that is configured for single user data entry, you will then find a way to obtain one or more lists of the documents that should belong to it, select all documents in the list, right click the code and select "Assign selected documents to this code".
How to obtain the list is a different matter, you could right click each "inclusion" code, "list items with this code" and then assign the list members to the allocation code. If you have more that one "inclusion" code you'll need to repeat the procedure for all of them, assigning the same item more than once to the allocation code will not create any problem.
Alternatively, you could walk the other way round, assign the approriate items to a single "exclusion" code and then use the search tab to find all documents "without this code". It is also possible to use the search tab (combining different searches with the "OR" boolean operator) to create one list of all items that have an "inclusion" code, or the reverse: all the items that have the exclusion codes. I will let you decide what is the fastest way as I don't know how your screening codes are organised.
In case the list(s) of items that you will be assigning to the allocation codes will contain more than 700 items, you will need to repeat the "select all & assign" procedure for all pages in the list. To speed up this, you may want to increase the page size, this is done through the "select the fields you want to display" button on the main documents page (the third button from the right) - the maximum is 4000 items per page.

The user manual explains how to create work allocations from page 42.  Note also that you could alternatively mark the excluded documents as "Excluded" or "Deleted" this will remove them from most lists, but will not actually delete any data: the only way to permanently remove items from a review is to "delete a source forever" (in the add/manage sources window). In other words, setting the "included/excluded/deleted" flag is a reversible operation that you may find useful for the current situation.

I hope this helps. Please feel free to ask for further clarifications.
Sergio