uncomment below line from src/views/layouts/main.vue.

 document.documentElement.setAttribute("dir", "rtl");
                                    

In order to have RTL mode enabled, uncomment last all RTL import files as mentioned below in the src/assets/scss/app.scss.
@import "custom/rtl/general-rtl";
@import "custom/rtl/bootstrap-rtl";
@import "custom/rtl/spacing-rtl";
@import "custom/rtl/float-rtl";
@import "custom/rtl/text-rtl";
@import "custom/rtl/structure-rtl";
@import "custom/rtl/plugins-rtl";
@import "custom/rtl/components-rtl";
@import "custom/rtl/pages-rtl";