Dear Nutsy_23,
Thanks for your updates and sharing the solution here. We appreciate it as it may help other community members who are experiencing the similar issues.
Besides the long formula, the better way I can consider may be to use the dependent drop-down lists solution in Power Apps.
For example, you have one source list ListDemoB and another list ListDemoA for you and users to update the data based on ListDemoB.
In ListDemoA, Column1 is to populate Likelihood from ListDemoB, Choice1 is a single-line text column populate Major, Minor and Moderate from ListDemoB and Column2 is a single-line text column to populate values from Major, Minor and Moderate from ListDemoB.


You can create a canvas app as follows.

TextInput2 for Title: Default:""
Dropdown1 for Column1: Items: Distinct(ListDemoB,Likelihood)
Dropdown2 for Minor: Items: Distinct(Filter(ListDemoB,Likelihood=Dropdown1.Selected.Result),Minor)
Dropdown3 for Major: Items: Distinct(Filter(ListDemoB,Likelihood=Dropdown1.Selected.Result),Major)
Dropdown4 for Moderate: Items: Distinct(Filter(ListDemoB,Likelihood=Dropdown1.Selected.Result),Moderate)
Create three buttons.
Minor: OnSelect: Patch(ListDemoA,Defaults(ListDemoA),{Title:TextInput2.Text,Column1:Dropdown1.Selected.Result,Choice1:Label3.Text,Column2:Dropdown2.Selected.Result})
Major: OnSelect: Patch(ListDemoA,Defaults(ListDemoA),{Title:TextInput2.Text,Column1:Dropdown1.Selected.Result,Choice1:Label4.Text,Column2:Dropdown3.Selected.Result})
Moderate: OnSelect: Patch(ListDemoA,Defaults(ListDemoA),{Title:TextInput2.Text,Column1:Dropdown1.Selected.Result,Choice1:Label6.Text,Column2:Dropdown4.Selected.Result})
If users or you click on Minor and type the Title value, select the Column1 value, the corresponding Minor , Major and Moderate values will be popped up and update the Title value, the selected Column1 value, the Choice1 value and the Minor value in Column2 in ListDemoA.
In the same way, if you select Major or Moderate, the Major value and the Moderate value will be populated in Column2 as well.
Result:


For your reference: Create dependent drop-down lists in a canvas app
Thanks for your effort and time.
Sincerely,
Cliff | Microsoft Community Moderator
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