Run a spreadsheet in a separate instance?

I’ve a spreadsheet that I like to keep open at all times, but save (and auto-save) will take about 5 minutes, and during that time Calc is “not responding”, so I can’t use any Calc documents during that time. So I’m looking for a way that saving that one file does not impact my workflow on the other spreadsheets.

Running a separate instance of libre office for that file may be a solution, is that possible? Or any better ideas?
I don’t want to turn off auto-save.

You could run a portable version of LibreOffice just for that spreadsheet. As a separate installation you could configure it just for that spreadsheet

Not sure which operating system your are using, but using different user profiles separates different instances on Linux (no need for addiitonal installations of the software) - see the following excerpt from my Linux process list:

opaque@system:~> ps -ef | grep [s]office
opaque       2068  2031  5 11:30 pts/0    00:00:00 /opt/libreoffice7.1/program/soffice.bin -env:UserInstallation=file:///tmp/LibreOffice-7.1-DE-2021-07-19 --splash-pipe=5
opaque      32388 32359  2 11:29 ?        00:00:01 /opt/libreoffice7.1/program/soffice.bin --splash-pipe=5

Process 2068 has been started using a different user profile location (using -env:UserInstallation= command line option) while process 32388 describes the start of my default instance