Indexing a portable drive across two systems

I'm trying to keep a folder synced between two separate systems, a PC and a laptop. Using Robocopy, I'm able to quickly and efficiently copy any changes I make on my PC to my laptop's SSD by plugging said SSD into a USB port and running Robocopy. This seems to work, as on my PC the laptop's SSD appears to have the new information replace the old information.

However, when I plug the SSD back into my laptop and run searches there, it shows the old data. For example, any changes to metadata aren't reflected in the search results. If I manually navigate to the folder the file is contained in and check the metadata there, it is accurate to what I copied over from my PC. So the indexing, specifically, isn't up to date.

Unfortunately, the indexing window says "Indexing complete", even though it's inaccurate. This hampers my ability to freely edit data on one system and copy it over, because it looks like the indexing only updates on the system the file is updated on. I had hoped indexing would notice if a file has been updated since the last time the system was on and would update it, but that doesn't seem to be the case.

I'm rebuilding the index now, but since that takes in excess of an hour I was hoping someone might have a solution to this issue. For example, would it be possible to save a specific drive's index file to OneDrive, point there on both systems and keep the indexing up to date that way? Or is there a way to shortcut indexing to only rebuild for changed files since the last time the system was on?

Thanks.