From what I see, you don't need to create a bookmark list. At least not if you want to have the x highest caches of a certain region. You can perform a search with the above mentioned filter (Top Elevation Caches), do not use a profile but a region. This should be enough. Altough, it is not possible to search for a certain elevation range.
There is also the possibility to run an elevation macro in GSAK. However, I did a run and it did not update the Cache elevation at all, but this may be because I haven't used it in months, old version, whatever. Probably, this can be checked by someone who is more familiar with GSAK.