Create Table from adjusted date range based on slicer

You don't need to duplicate the Transactions table manually instead you can use a DAX calculated table or a measure that feeds into your table visual.

SPLY Transactions Table =
VAR __minDate = MIN('Date'[Date])
VAR __maxDate = MAX('Date'[Date])
VAR __startDate = DATE(YEAR(__minDate) - 1, MONTH(__minDate), DAY(__minDate))
VAR __endDate = DATE(YEAR(__maxDate) - 1, MONTH(__maxDate), DAY(__maxDate))

RETURN
FILTER (
ADDCOLUMNS (
'FinancialTrans',
"TransactionDate", RELATED('Date'[Date])
),
[TransactionDate] >= __startDate &&
[TransactionDate] <= __endDate
)

If Customer is in your FinancialTrans table or related to it, then clicking a customer in the matrix will contextually filter this table too.

Or you can use a measure :

Show SPLY Txn =
VAR __minDate = MIN('Date'[Date])
VAR __maxDate = MAX('Date'[Date])
VAR __startDate = DATE(YEAR(__minDate) - 1, MONTH(__minDate), DAY(__minDate))
VAR __endDate = DATE(YEAR(__maxDate) - 1, MONTH(__maxDate), DAY(__maxDate))

RETURN
IF (
'FinancialTrans'[Date] >= __startDate &&
'FinancialTrans'[Date] <= __endDate,
1,
0
)

Then use a visual-level filter on the table to show only rows where Show SPLY Txn = 1.