Can I customize workflow start up window, I need to add more fields in the same pop window like this:Please suggest.
Like most things in AEM - this can be modified. However - we do not have any examples on how to do this.
It depends where you want to add those option to start workflow, for example if you want to modify start workflow trigger from sites
then you can overlay /libs/cq/gui/content/common/startbulkworkflows/body/items/form/items/wizard/items/properties/items/fixedColumnContainer/items/fixedColumn/items