Consider [Rolling Stone: 500 Greatest Albums of All Time: 2012 edition|https://musicbrainz.org/series/8668518f-4a1e-4802-8b0d-81703ced6418]
and the [Rolling Stone: 500 Greatest Albums of All Time: 2020 edition|https://musicbrainz.org/series/6a4b53b9-2756-4afe-93f2-306039d41910]

What I’d like to be able to see is an additional column on the 2020 page showing the position difference since 2012 - same as you would have on a weekly sales chart show last weeks position (^3, v5, -, etc).

I wrote some python to do what I wanted: https://github.com/a74nh/tastybrianz 

Rolling Stone: 500 Greatest Albums of All Time: 2020 edition
| num    | title                    | artist             | year   | rs2012   
|--------+--------------------------+--------------------+--------+----------
| 1      | What’s Going On          | Marvin Gaye        | 1971   | ^5       
| 2      | Pet Sounds               | The Beach Boys     | 1966   | -        
| 3      | Blue                     | Joni Mitchell      | 1971   | ^27      
| 4      | Songs in the Key of Life | Stevie Wonder      | 1976   | ^53      
| 5      | Abbey Road               | The Beatles        | 1969   | ^9       
| 6      | Nevermind                | Nirvana            | 1991   | ^11      
| 7      | Rumours                  | Fleetwood Mac      | 1977   | ^19      

Here I can see Joni has moved up 27 spots from the 2012 list to the 2020 list

However, it'd be great if there was a way on musicbrainz to associate a series with another series.

Series are used in multiple ways on musicbrainz. So maybe instead there could be a "chart" object which is like a series but it's describes an ordered list. Charts could then be easily compared with other charts.