From what I understand, you want to check if there is an arrow somewhere in the last 8 candles. Only for custom indicators you have extra options in the Condition block. Try this option:
0_1523045805157_730d20fa-eda2-455f-a6ff-4bd9bcc91f20-image.png
I didn't tested it, but it should work, because if the highest value is EMPTY_VALUE, the Condition block itself would not pass if either value equals to EMPTY_VALUE.
Otherwise you can try this block - Indicator moves within limits. This block and these special options in Condition are the only places in the EA builder where some indicator values in the past can be checked.