Should I choose "Multiple States" from the drop down re: 1099-DIV Box 12 if there are so many "it would take hours to enter", per the dividend payer?

You can, if the amount is so small you are not concerned about extra state tax, see below.   The dividends/interest reported there won't be taxed on your federal return.  However, Colorado taxes dividends/interest paid by another state.

You can select Multiple States from the dropdown if you:

• Live in a state with no income tax (AK, FL, NV, SD, TN, TX, WA, WY)
• Live where exempt-interest dividends from other states aren't taxed (DC, IN)
• Have only a small amount of exempt-interest dividends and aren't concerned with extra state tax
  • Your state (CO) will tax these dividends or interest if you don't live in an area listed above.

You can find the state on more detailed documents (like supplemental forms) from your financial institution/dividend payer.

@sandyhaller2    If the amount you calculate, that is from CO bonds and is up-to, say $50-100 or more...then you could break out the CO $$ amount (And any US Territories too).    But all the other states are lumped together as one value...."Multiple States"

Example on how to do it is shown below from Desktop software.....online would look similar:

_________________________________