[Chimera-users] How to subgroup the chains of oligomer pdb

Friends I would like to learn how to subgroup the chains of a oligomer pdb. suppose i have a pdb with chain A to L, in which A,B,C,D,E,F belongs to gp20 and G,H,I,J,K,L belongs to gp20. My question is how to add the descriptions to these groups chains so that when the viewer look the pdb file when he selects the gp20 all the chains to this group are selected A-F. Please give your feedback if chimerax can do it, how to do it?