Hello @TimurShangareev,
Following Example 25.8 Changing Titles by Using the %GrTitle Macro from the SAS documentation I accomplished the change by inserting these two statements before the PROC MIXED step:
%grtitle(path=Stat.Mixed.Graphics.ResidualPanel)
%let Mixed_ResidualPanel = Studentized Residuals for Change from Baseline;
By deleting the above macro variable using
%symdel Mixed_ResidualPanel;
you can revert to the default title.