In my point of view, to define nonlinear behavior of shear-link for eccentrically braced in ETABS, you must use Hinge Properties and then assign plastic hinges that you defined to the shear-link.
also, I strongly recommend you to use SAP2000 or PERFORM 3D instead of ETABS. because SAP2000 and PERFORM 3D are provided to solve nonlinear problems
Sir, I can model the shear moment behavior in sap2000 by using multilinear plastic link property but which model should I use for the hysteresis curve as there are many given.
You have to define two shear hinges at the end of your link beam.
You need a constitutive model for the shear-deformation curve; for this purpose you can use the model proposed by Richards, P. "Testing Protocol for Short Links in Eccentrically Braced Frames", 2006. You can simply calculate the shear spring properties by this method and assign it to the model.
you should be able to perform nonlinear analysis on the shell elements if you define the sections as "Define--> Area sections --> add new section --> Shell layered/nonlinear". When you select "Modify layer definition", you can set all the components as nonlinear (or just set those that you need).
also you can find helpful information in following Links
https://www.youtube.com/watch?v=JqE-nQjeUGs
https://www.youtube.com/watch?v=Y7z6IYxF-eQ
also you can connect to Mr Brisid Isufi he was work on nonlinear Shell Elements in SAP2000