There is a Granth called 'beejak' which contains poetry of kabir jee which is not in Guru Granth Sahib. It can be bought at
https://www.amazon.in/Kabeer-Beejak-Swami-Anand-Kulshreshtha/dp/9351653978/ref=asc_df_9351653978/?tag=googleshopmob-21&linkCode=df0&hvadid=397119259345&hvpos=&hvnetw=g&hvrand=15132795166450457460&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9303784&hvtargid=pla-912828598927&psc=1&ext_vrnc=hi
It's free on unlimited kindle membership.
History says that ramanand ji was kabir jee's Guru and in Guru Granth Sahib, kabir ji mentions having a Guru or Satguru.
But in beejak Granth, kabir ji mentions that ramanand worships Raam, the son of Dasrath whereas kabir worships raam(Vaheguru) who is present in every heart.
Kabir ji says that I have tried to explain this to ramanand(to give up worship of raam, the son of dasrath) again and again but he does not listen to me.