suggest a query to write in Google Sheets to achieve the basis of the following

Have 2 Fields- Lead Stage & Lead Disposition

Relation or Dependency- Lead Stage to Lead Disposition

Objective- If I select a specific Lead Stage, as per mapping only the mapped option should be available in Lead Disposition to select & not all

Example- I have Qualified as a Lead Stage, & when I select the same, as per mapping only New is the Option available & only that should be available in the Lead Disposition to choose from

Following is the Query, which I am sure about

However, the challenge is how to do this in the Validations Option, as for a particular Lead Stage I have only 1 Lead Disposition Mapped but for certain there are many

For Example

Lead Stage- Open
Lead Disposition- New
In this the above mentioned formula can definitely work, & in a Cell, I do not need to do that in Validations & in Custom Formula option

But now lets look at this

Lead Stage- Qualified
Lead Disposition- Indian Compliance, Global Compliance, Wealth & Finance Management | Investments & Loans
Now in this case I have 3 possible scenarios, which is restricting me from applying the same in a cell & I have an option to do that with the help of Validation, Custom Formula is

But when I do that, it does not give me any option to select, because in Criteria I have to Select Custom Formula is, & I have no option to use Dropdown or Dropdown from a Range