One of the questions hanging over the computation of the 2017 UEFA coefficients has been how they would affect the 2018-9 qualifying, given that major changes are coming to the Champions League, and by extension, the Europa League.
For 2017-8, entry is determined by the 2016 coefficients. There is a table put together by the indispensable Bert Kassies that shows what happens to a nation's teams at various rankings. In the range of realistic interest for Scotland, countries 13-15 are equivalent, 16 and 17 are, 18-24 are, and 25 down to 45 are.
In other words, if your national coefficient drops from 15 to 16, your league champion enters a round earlier, your second place team enters the Europa League rather than the Champions League, your third-place team enters in the first round of Europa League qualifying rather than the third, and your fourth-place team doesn't get to play European football. (That's a big deal!)
If your coefficient drops from 17 to 18, your national cup winner enters in the second round rather than the third, and your second-place team enters in the first round.
If your coefficient drops from 24 to 25, your cup winner also enters in the first round. (Scotland landed at 25 for 2016. It is possible this will get reshuffled to spare their cup winner the first round matches.)
This month, UEFA approved the new access list for 2018/9 qualifying. Unfortunately, they then neglected to release it. So it fell to Kassies to piece it together from publicly-available information and leaks on his message board. Based on his list, the breakpoints are in the same places.
The differences are what happens at those breakpoints. The drop from 15 to 16 only pushes your third-place team back one round, since they were only getting to enter in the second round anyway. The drop from 17 to 18 makes your national champions enter in the first round of Champions League qualifying. (Previously the first round was only for the lowest-ranked associations; there's a new pre-first round for them.)
So, how does this affect Scotland? For 2018/9, not much. If the Cypriot and Bulgarian teams both have amazing runs through the Europa League knockout phase, Scotland could conceivably be knocked down to 25th again. But that is very unlikely.
From 2019 onward, aside from avoiding that 24th/25th drop, now a climb to 17th is even more important, as it spares the national champions one extra round of qualifying. Unfortunately, they would have to make up almost 5 points on Denmark in next year's competitions (as well as lesser amounts on other teams) to get up there. For 2020, however, they need less than 4 points on Austria -- and they have two years to do it. Two years of solid performances by Celtic and Rangers could have them within striking distance. 2021? Well, by that point, the rules will most likely change again.