WIP add global variables for custom workflow

[dianqihanwangzi]

Signed-off-by: guoyu [email protected]

What this PR does / Why we need it:

What is changed and how it works?

Does this PR introduce a user-facing change?

• [ ] API change
• [ ] database schema change
• [ ] behavioral change
• [ ] change in non-functional attributes such as efficiency or availability
• [ ] fix of a previous issue