Its complicated to explain in the forum, and I do not want to rewrite the online doc in a post. You can use panel contexts to create different sets of configs:
[mycontext]
user=xxxx:yyyy:zzzz
buttonfile=mycontext-buttons.cfg
[myothercontext]
user=aaaaaa:bbbbb:ccccc
buttonfile=myothercontext-buttons.cfg
If you use freepbx and you only want to limit some users so they can view some of the buttons and not all, install the fop2admin freepbx module where you will be able to manage groups. Groups are also explained in the docs, basically
group=mygroup:SIP/100,SIP/200
user=1111:supersecret:all:mygroup
Where user 1111 will only see SIP/100 and SIP/200