If you want to have more than 10 Simultaneous Transfers in Filezilla I have found editing the following two files worked for me.
First make a backup of any files you are going to edit.
Edit your filezilla.xml config file and search for the line which specifies the Number of Transfers, should read like this:
<Setting name="Number of Transfers">10</Setting>
Change the 10 to, say 40. Save file.
Edit your sitemanager.xml config file and search for the line in the list of servers for the server you connect to and wish to increase the number of connections whilst transferring files. The line you’re looking for might read like this:
Change the 0 (or what value you have) to 40. Save file. Close files you have edited.
Connect to the server and you should (if all goes well) be able to simultaneously download more than ten files at a time using Filezilla.
This is what works for me.