Stocks redistribution Table

Here's the solution:

You use the Filter Pane of the table above with the [Is True Target Store] measure to obtain the above.

And here's what needs to be created in PQ behind the scenes:

// SalesAndStockBaseTable
let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WCi7JL0pVMDBU0lFyBGIgMlWK1YGLG0HFjUFySOLGUHEjdA0mSBLI4qYIC8yRxc2AAk4QcWRhc6iwKZq4BUK5oRGyhCVWcwwNEMLGSrGxAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"Store ID" = _t, ProductID = _t, #"Sales Qty" = _t, #"Stock Qty" = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Store ID", type text}, {"ProductID", type text}, {"Sales Qty", Int64.Type}, {"Stock Qty", Int64.Type}}),
    #"Added Custom" = Table.AddColumn(#"Changed Type", "Store Type", 
        each 
        let
            StockQty = if [Stock Qty] = null then 0 else [Stock Qty],
            SalesQty = if [Sales Qty] = null then 0 else [Sales Qty],
            Output = 
                if StockQty > 0 and SalesQty = 0 then "Source Store" 
                else 
                if StockQty = 0 and SalesQty > 0 then "Target Store" 
                else 
                    "Neutral Store"
        in
            Output
    )
in
    #"Added Custom"

// Stores
let
    Source = SalesAndStockBaseTable,
    #"Removed Other Columns" = Table.SelectColumns(Source,{"Store ID", "Store Type"}),
    #"Removed Duplicates" = Table.Distinct(#"Removed Other Columns")
in
    #"Removed Duplicates"

// Products
let
    Source = SalesAndStockBaseTable,
    #"Removed Other Columns" = Table.SelectColumns(Source,{"ProductID"}),
    #"Removed Duplicates" = Table.Distinct(#"Removed Other Columns")
in
    #"Removed Duplicates"

// Target Stores
let
    Source = Stores,
    #"Filtered Rows" = Table.SelectRows(Source, each ([Store Type] = "Target Store")),
    #"Removed Columns" = Table.RemoveColumns(#"Filtered Rows",{"Store Type"}),
    #"Renamed Columns" = Table.RenameColumns(#"Removed Columns",{{"Store ID", "Target Store ID"}})
in
    #"Renamed Columns"

// Sales and Stock
let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WCi7JL0pVMDBU0lFyBGIgMlWK1YGLG0HFjUFySOLGUHEjdA0mSBLI4qYIC8yRxc2AAk4QcWRhc6iwKZq4BUK5oRGyhCVWcwwNEMLGSrGxAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"Store ID" = _t, ProductID = _t, #"Sales Qty" = _t, #"Stock Qty" = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Store ID", type text}, {"ProductID", type text}, {"Sales Qty", Int64.Type}, {"Stock Qty", Int64.Type}}),
    #"Added Custom" = Table.AddColumn(#"Changed Type", "Store Type", 
        each 
        let
            StockQty = if [Stock Qty] = null then 0 else [Stock Qty],
            SalesQty = if [Sales Qty] = null then 0 else [Sales Qty],
            Output = 
                if StockQty > 0 and SalesQty = 0 then "Source Store" 
                else 
                if StockQty = 0 and SalesQty > 0 then "Target Store" 
                else 
                    "Neutral Store"
        in
            Output
    ),
    #"Removed Columns" = Table.RemoveColumns(#"Added Custom",{"Store Type"})
in
    #"Removed Columns"

Current Stocks = 
var StoreInScope = ISINSCOPE( Stores[Store ID] ) 
var ProductInScope = ISINSCOPE( Products[ProductID] )
var BothInScope = StoreInScope && ProductInScope
var Result =
    if( BothInScope,
        sum( 'Sales and Stock'[Stock Qty] )
    )
return
    Result

Is True Target Store = 
var SourceStoreInScope = ISINSCOPE( Stores[Store ID] )
var SourceStoreIsReallySource = 
    SELECTEDVALUE( Stores[Store Type] ) = "Source Store"
var TargetStoreInScope = ISINSCOPE( 'Target Stores'[Target Store ID] )
var TargetStoreNotBlank =
    // It could be blank due to the additional row
    // generated by DAX in the Target Stores table
    // after enabling the relationship which has
    // referential integrity violations (but this is
    // how it should be since not all stores are
    // target stores).
    NOT ISBLANK( SELECTEDVALUE( 'Target Stores'[Target Store ID] ) )
var ProductInScope = ISINSCOPE( Products[ProductID] )
var AllThreeInScope = TRUE()
    && SourceStoreInScope
    && SourceStoreIsReallySource
    && TargetStoreInScope
    && TargetStoreNotBlank
    && ProductInScope
var IsCurrentTargetStoreForCurrentProduct =
    if( AllThreeInScope,
        CALCULATE(
            NOT ISEMPTY( 'Sales and Stock' ),
            // Remove filters from Stores
            ALL( Stores ),
            // Enable filtering from the Target Stores
            USERELATIONSHIP(
                'Target Stores'[Target Store ID],
                'Sales and Stock'[Store ID]
            )
        )
    )
return
    // I multiply by 1 to return an int
    // so that the Filter Pane can work
    // with this measure.
    1 * IsCurrentTargetStoreForCurrentProduct