That is a limitation of the current version of the addon.
I hope to update the Firefox version of this addon to have the same features of the Chrome extension (Including the ability to save lists of links). However it will take some time as API's differ between Chrome and Firefox. Hopefully I will have it done soon though.
I am still testing this extension, but this is easy code and should work fine. Error correction on loading bad url lists is something to watch. Keep history of lists loaded. option to set 10, 20, 50, 100 lists saved, I personally save my data in way too many places, I am on folder overkill except for my downloads, those go into one folder and then I move to different storage devices. I will update this after I do so mass url save/loads. Thank you. FIBER0PTIC/FBR, The HUMBLE Guys, Napalm & Worship Inc.