Add (expand list) value from dropdown list to multidropdown

[alcompstudio]

Hi, respected Bubble experts!

I got a problem, please need some help!

I have 3 things (DB tables):

1. Milestones
2. Bids
3. Contractors.

Milestones and Bids use a relationship with Contractors. Milestones have a multidropdown field where Contractors are selected (multiple values), and Bids have a dropdown field where Contractors are also selected (single value).

I need to create a Workflow, (button click in Bids) so that the Contractor (dropdown field value) existing in the Bid is “added” (joined) to the multidropdown field in the Milestone and save in DB new list. In doing so, you don’t need to add a new value to the Contractors Thing, but rather have the existing “contractor” simply appear as another value in the multidropdown. Below is a sample screenshot.

Can you give me any hints on how to do this? I’d be happy to have any hints ).

[alcompstudio]

I basically don’t need to display the value on the page in the multidropdown. I need the value to appear in the Milestone Thing in the multidropdown field when the button is clicked.