The deep linking URLs are partially customizable as per this FooPlugins article which will show you how to create a custon prefix.
https://fooplugins.helpscoutdocs.com/article/62-deeplinking-in-foobox-pro
The rest of the URL is not customizable at this stage and is made up of the following format:
#{option_value}-{foobox_id}/{item_index}/{item_identifier}
option_value – This is the prefix value entered into the FooBox Settings.
foobox_id – This is a page specific instance id for FooBox, basically an integer that is incremented by one for every instance of FooBox created in a page.
item_index – This is the item specific index within the FooBox modal. FooBox can display multiple items with previous/next buttons so this is just an index pointer to the specific item within it items array.
item_identifier – This is an item specific identifier that is used to try lookup the item before falling back to the index, this is to handle item index changes.
