Vertical Multiple Dependent Drop-down List, 2nd layer inquiry

Hello again good people of Excel Forum,

Attached is my WIP Master_On-site event itinerary excel.

Event Itinerary MASTER_SAMPLE.xlsx

I am able to create the first rundown with an easy [NAME RANGE] separating them into 2 groups (Production) & (Operation).

Within the 2 groups, there are different type of vendors;
and within each different type of vendor, we usually have 3 or more different companies.

But I cant seem to get the 2nd layer of drop-down list to work.
I have highlighted the areas in yellow on my [MASTER Template] tab, and also on [Vendor List] Tab.
These are the areas where I need them to link and show up on my [MASTER Template]. Please help.

*Moving forward, we will proceed to also work with other vendors and would like to also include them into the list.
So ideally the used [Data Validation] formula would be fixed on the highlighted square areas (empty areas included) so that when I insert a new row within it would still be able to detect, or just a simple full column detection with the # formula?

Thank you!

Administrative Note:

Please include formulae used in your post in addition to providing a workbook (for the benefit of members unable to download attachments).

Thanks.