Not sure if this would be considered the same as/similar to this inquiry from a few years ago (https://dojo.domo.com/t5/Card-Building/How-do-I-add-a-trend-line/m-p/6573#M344) but we haven't been able to locate a Regression Line section in chart properties within Analyzer to try that (deprecated?).
What we're looking to do is "reverse" the positive/negative progression of the line value scale - instead of trending in a downward direction as the number increases or upward when it decreases, we'd like it to trend opposite depending on what's happening.
EXAMPLE: between March 2018 and April 2018, it went from $41k to 65k and the line trended downward but we'd like it to go in the other direction - then, between April 2018 and the current month (May 2018), it goes from $65k to $15k but that's actually a negative direction, so we'd like it to trend downward instead of up. In both instances, they are negative numbers so we want that aspect to remain the same, just have them trend in the opposite direction.

Does that make sense?