Thank you firstname.lastname@example.org
Task manager and Resource monitor are two Windows tools to determine what your computer is doing. Normally I sort in inverse order by cpu usage so the most usage tasks are on top. If your CPU usage is high, then too much stuff is running.
When Scrivener shows "No response" its CPU usage is about 10, 15 %. The CPU usage in total for example about 30, 50 %.
You can also check disk usage to see if you are having difficulties with your drive(s)
At the moment - Scrivener properly works - the Resource Monitor shows this:
Where are you storing your data? Your image shows a 256GB SSD drive and a huge usb drive. If the data is being stored on the external usb drive, it will be slow. If it is being stored on your SSD it should be lightening fast. If you are trying to store in the cloud, give it up.
Actually usually when storing the data on the external drive it is fast enough. Data stored on the SSD often are not processed faster. I do not use online storage.
Also you need to determine whether you are out of memory. You have 8 GB of ram so there it is unlikely that you would be running out unless something was wrong, but task manager or resource monitor will tell you if your ram usage is over 70%.
The sluggish behavior of Scrivener does not appear to have a connection to the RAM usage. When the usage of RAM is under 70 %, e.g. 50 % or less Scrivener can run sluggish as well.
Finally, try closing the machine and then restarting. Do not open any other applications. Now try Scrivener. How does it work? Do you still have the problems?
Scrivener sometimes first runs well, after some time it does not anymore, then after some time it runs well again in the same session (without restarting the system). So I could imagine checking how Scrivener runs after a reboot might not be that expressive. It seems as if Scrivener after a restart of the system runs well, sometimes it does not.
When the language of Scrivener is switched to an other language than English it always seems to be sluggish, slow.