I am not sure you can avoid warnings with a quad mesh at the corner. What you are currently getting are probably warnings meaning you will be able to continue the analysis. The modeling and meshing guide ( https://ansysproducthelpqa.win.ansys.com/account/secured?returnurl=/Views/Secured/corp/v232/en/ans_mod/Hlp_G_ModTOC.html ) details various controls. MSHOPT and MSHKEY may be the primary commands you can use to control. I think by changing the number of divisions on the longer lines (coarsening) you may be able to get less warnings. But may be you should consider using a TET mesh or extruded triangular prisms.
You are navigating away from the AIS Discovery experience