Use one SharePoint List to populate another based on selection; Neophyte seeking assistance

[huuvola]

I have two (2) SharePoint lists. I want one to feed line item information the other...

One is "Master" it contains all the information related to a single line item; 

Master_Title, Master_Section, Master_Number, Master_POC, etc.. 

The Second is "assignments" (like entering a Help Desk ticket...); Requestor, Request_Date, Due_Date, etc.  It ALSO contains fields to record what "Title", "Section", "POC" etc. from the Master SPO list... so, when a person is entering the "Assignment" they would be offered a drop down to select from- which would refer back to the "Master" list and give them a list of all the available "Master_Titles" in the Master list from which to select.  The selection of any "Master_Title" on the Assignments list/form would then instantly populate other fields in the "Assignment" list/form (not populate upon Save or other command- but populate those fields as soon as an initial selection is made) for "Section", "POC", etc. that are included on that Master_Title's line item entry.  Multiple line item entries on Assignments will refer to a single line item on Master.  The Master does not keep track or record or do ANYTHING but feed data fields into Assignments. I don't want the Master list to contain ANY information from Assignments.. only to feed the line items entered.  

Further, this needs to be set up such that a future Assignments list based PowerBI report can be created to report both the data manually entered and the line item data pulled from Master in list Assignments to a dashboard... so, the data fed to it from Master should STAY in the Assignment list (?).  

WARNING!!! I don't even know how to build the Forms in PowerAps as yet... so, this request is especially loaded with landmines.. first, I need to know from which list to initiate the form building (Assignments?), then how to add the second list ("Master"?) as a data feed (?)...

I think "neophyte" is a huge understatement.  Thank you all for any kind assistance. -huuvola

[RandyHayes]

@huuvola 

So, your Form would be based on the Assignments list as that is where you are going to create the records.

In your form, you will have a field for the Title, Section and POC (as they are part of your record).

First question I have is - is this really going to be the Title of the record in the Assignments?  It's okay, but just asking.

Next you will change your Title column type to an Allowed Values type column (this is done as soon as you add the Title field to your form in the Control Type selection).

Then you will change the Items property of the dropdown that it provides automatically.  That will be set to Master

You will then display the column from Master that you want to appear in the dropdown.

Finally, the Section and POC columns in your form will derive their values from the Title control.

So, for example, the Section (assuming Text) will have a Default property on the DataCardValueX column (which will be a TextInput) of DataCardValueX.Selected.Master_Section  (where DataCardValueX is the control that is the dropdown control in the Title field).

You would do the same for the POC.

So, being new at this, you will have some fun learning how to make this happen.  Keep it simple as you go and it will go easily.

I hope this is helpful for you.

[huuvola]

It'll be a couple days before I get to try this out.. then I'll happily mark as Accept as Solution!  🙂  THANK YOU!

[RandyHayes]

@huuvola 

Or ask more questions!!  Since you state you're new to this, there might be a lot of blanks to fill in from what I mentioned...so, ask as needed!

AND - thank you for the coffee!!  Love the stuff! ☕