I worked through March in OR (income tax). After that and going forward I work from home in WA (no income tax). Taxes are being paid in WA, how do I set this up?

No one will know exactly, until your company issues your W-2 for 2020 next January.

If the payroll department is on the ball, they will only show your wages thru March as OR income in boxes 15,16,17 of that W-2.  Then you will file an non-resident OR tax return for that OR income as you usually do, but for that lower amount of OR wages.

They "might" also show a second line for boxes 15,16,17   with WA in box 15, and the last 9 months of wages in box 16 and nothing in 17 ......but I'm uncertain if this second part is SOP for a W-2, or perhaps optional since WA has no income tax .

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AND...the Most Oregon forms are not "expected" to be available in the software until well into January, (supposedly the 14th, but TTX could change that to a later date in the next few weeks).  Don't bother filing Federal nor Oregon tax forms until well into February at the soonest.

https://ttlc.intuit.com/community/forms/help/state-forms-availability-table-for-turbotax-individual-personal-tax-products/00/26227