I found an previous thread that show example on how to add custom option under actions-dropdown using record action. And thanks, at least it is something working on the customization finally 
(SuiteCRM 8.7 Detail View Button Implementation: Help with Authorization Error - #10 by Harshad)
Just wondering if it is still possible to add button in the same row of the “Edit” button (before/after)? I searched through forum and some oldest thread guided on adding custom button in the detailviewdefs.php. However, I tried different ways but it is not working. Just to confirm if it is still feasible or not?
Hope to hear from you guys soon. Thanks
SuiteCRM Newbie 