From skimming the help page on Indexing (https://pro.arcgis.com/en/pro-app/latest/help/projects/update-the-search-index-for-project-items.htm), it looks like it should be able to pause & resume, even when it hits the memory limit, I think?
So I guess dumb question first: Each time it stops and you restart, are you sure that it's starting from scratch, or is it resuming its progress and getting further each time?
Another thought would be whether the specs on the networked drive (or the network connection, itself) might be the bottleneck. Because the specs on your end theoretically shouldn't be a bottleneck, unless Pro isn't using all of the available resources.
I'm kinda surprised I haven't found anything on this page about increasing the allocated memory, but it might be there and I just haven't found it.
